Patent Application
20140287208
Electroless composite technology is a more recent development as compared to electrolytic composite technology. The fundamentals of composite electroless plating are documented in a text entitled “Electroless Plating Fundamentals and Applications,” edited by G. Mallory and J. B. Hajdu, Chapter 11, published by American Electroplaters and Surface Finishers Society (1990).
The plating of articles with a composite coating bearing finely dispersed divided particulate matter is well documented. This technology has been widely practiced in the field of electroplating as well as electroless plating. The acceptance of such composite coating stems from the recognition that the inclusion of finely divided particulate matter within metallic matrices can significantly alter the properties of the coating with respect to properties such as wear resistance, lubricity, friction, thermal transfer, and appearance.
The evolution of composite electroless plating dates back to Oderkerken U.S. Pat. No. 3,644,183 in which a structure of composite electroless plating with finely divided aluminum oxide was interposed between electrodeposited layers to improve the corrosion resistance. Thereafter, Metzger et al., U.S. Pat. Nos. 3,617,363 and 3,753,667 extended the Oderkerken work to a great variety of particles and miscellaneous electroless plating baths. Thereafter, Christini et al. in Reissue U.S. Pat. No. 33,767 further extended the composite electroless plating to the codeposition of diamond particles. In addition, Christini et al. demonstrated certain advantages associated with the deposition of the barrier layer (strike) prior to the composite layer.
Feldstein in U.S. Pat. Nos. 4,358,922 and 4,358,923 demonstrated the advantages of utilizing a metallic layer above the composite layer. The overlayer is essentially free of any particulate matter. Spencer in U.S. Pat. No. 4,547,407 demonstrated the utilizing of a mixture of dual sized particles in achieving improved smoothness of coating.
Feldstein et al. in U.S. Pat. Nos. 4,997,686, 5,145,517, 5,300,330, 5,863,616, and 6,306,466 demonstrated utilization of particulate matter stabilizers in the deposition of uniform stable composite electroless plating. Parker in U.S. Pat. No. 3,723,078 demonstrated the codeposition of refractory metals and chromium along with composite electroless plating.
Helle et al. in U.S. Pat. Nos. 4,098,654 and 4,302,374 explored special surfactant compositions in the preparation of stabilized PTFE dispersions and their subsequent utilization in electrolytic plating.
Kurosaki et al. in U.S. Pat. No. 3,787,294 proposed the use of cationic stabilizers for graphite fluoride be used in electroplating with specific attention focused upon surfactants having a C—F bond in their structure.
Brown et al. in U.S. Pat. No. 3,677,907, demonstrated the utilization of surfactants also having a C—F bond in their skeleton used in combination with PTFE electrolytic codeposition.
Henry et al. in U.S. Pat. No. 4,830,889, demonstrated the utilization of a cationic fluorocarbon surfactant along with a non-ionic fluorocarbon surfactant for the codeposition of graphite fluoride in electroless plating baths.
Feldstein et al. in U.S. Pat. No. 5,580,375 also demonstrated the use of “frozen states” to overcome the limited shelf-life associated with certain dispersions before their use in plating applications.
Kanai in U.S. Pat. No. 4,677,817 demonstrated travelers with composite carbide coatings for use in ring spinning.
Nakano et al. in U.S. Pat. No. 4,698,958 demonstrated rings with a ceramic coated layer for use in ring spinning.
Feldstein in U.S. Pat. No. 5,721,055 demonstrated benefits of composite coatings with lubricating particles on spinning textile machinery parts.
Feldstein in U.S. Pat. No. 6,309,583 demonstrated the ability to enhance the thermal transfer properties of articles coated with various composite coatings.
Feldstein et al. in U.S. Pat. No. 6,506,509 demonstrated the ability to and utility of producing composite layers with varying densities of codeposited particles in the plated layer along the surface of the substrate.
The following patents are noted for their schematic drawings for the machinery parts of interest in this invention.
Schmid in U.S. Pat. No. 5,164,236 describes the coating of open-end rollers with a metal-carbide coating with a nickel overlay thereof. The metal-carbide is deposited by a plasma coating approach.
Herbert et al. in U.S. Pat. No. 4,193,253 describe the coating of OE rotors with a silicon carbide composite coating.
In addition, Kenai in U.S. Pat. No. 4,677,817 and Nakano at al. in U.S. Pat. No. 4,698,958 illustrate well certain parts useful in ring spinning.
The co-deposition of particles in composite electroless plating can dramatically enhance existing characteristics and even add entirely new properties. These capabilities have made composite electroless coatings advantageous for a variety of reasons including, but not limited to, increased utility in conditions requiring less wear and lower friction; facilitating the use of new substrate materials such as titanium, aluminum, lower cost steel alloys, ceramics, and plastics; allowing higher productivity of equipment with greater speeds, less wear, and less maintenance related downtime; and replacing environmentally problematic coatings such as electroplated chromium. In this last regard, for example, composite electroless coatings with nickel provide an additional environmental advantage over conventional electroless nickel coatings, which do not include particulate matter, in that the particles within composite electroless nickel coatings reduce the amount of nickel alloy used. Specifically, composite electroless nickel plating reduces the amount of nickel introduced to the environment by a percent equal to the volume percent of the particulate matter within the composite electroless nickel coating.
In addition, composite electroless coatings may be regenerative, meaning that their properties are maintained even as portions of the coating are removed during use. This feature results from the uniform manner with which the particles are dispersed throughout the entire plated layer.
Specifically, “electroless” nickel is an alloy of nominally 88-99% nickel and the balance with phosphorous, boron, or a few other possible elements. Electroless nickel is commonly produced in one of four alloy ranges: low (1-4% P), medium (6-8% P), or high (10-14% P) phosphorous, and electroless nickel-boron with 0.5-3% B. Each variety of electroless nickel thus provides properties with varying degrees of hardness, corrosion resistance, magnetism, solderability, brightness, internal stress, and lubricity. All varieties of electroless nickel can be applied to numerous articles, including metals, alloys, and nonconductors.
The metal portion of the metal salt may be selected from suitable metals capable of being deposited through composite electroless plating. Such metals include, without limitation, nickel, cobalt, copper, gold, palladium, iron, other transition metals, and mixtures thereof, and any of the metals deposited by the autocatalytic process in Pearlstein, F., “Modern Electroplating”, Ch. 31, 3rd Ed., John Wiley & Sons, Inc. (1974), which is incorporated herein by reference. Preferably, the metals are nickel, cobalt and copper. Generally, the electroless metal in the deposited coating is a metal or a metal alloy, usually in the form of a metal, a metal and phosphorous, or a metal and boron. The metal or metal alloy is derived from the metal salt used in the bath. Examples of the metal or metal alloy are nickel, nickel-phosphorous alloy, nickel-boron alloy, cobalt, cobalt-phosphorous alloy, and copper. Other materials such as lead, cadmium, bismuth, antimony, thallium, copper, and others may be included in the coating of the present invention.
The salt component of the metal salt may be any salt compound that aids and allows the dissolution of the metal portion in the bath solution. Such salts may include without limitation, sulfates, chlorides, acetates, phosphates, carbonates, sulfamates.
The reducing agents are electron donors. When reacted with the free floating metal ions in the bath solution, the electroless reducing agents reduce the metal ions, which are electron acceptors, to metal for deposition onto the article. The use of a reducing agent avoids the need to employ a current, as required in conventional electroplating. Common reducing agents are sodium hypophosphate, sodium borohydride, n-dimethyl borane (DMAB), n-diethylamine borane (DEAB), formaldehyde, and hydrazine.
The particulate matter may be any suitable particle that is typically used in composite electroless plating. Preferably, such particulate matter is insoluble or sparingly soluble within the plating solution. It is also preferable that the particulate matter be inert and non-catalytic with respect to the deposition process. Particulate matter suitable for practical composite electroless plating may be from nanometers in size up to approximately 75 microns in size. The specific preferred size range depends on the application involved.
The particulate matter may be selected from a wide variety of distinct matter, such as but not limited to ceramics, glass, talcum, plastics, diamond (polycrystalline or monocrystalline types), graphite, oxides, silicides, carbonate, carbides, sulfides, phosphate, boride, silicates, oxylates, nitrides, fluorides of various metals, as well as metal or alloys of boron, tantalum, stainless steel, molybdenum, vanadium, zirconium, titanium and tungsten. Without limitation, preferred specific examples of particulate matter for use in the present invention are polytetrafluoroethylene (PTFE), diamond, silicon carbide, boron nitride (BN), aluminum oxide, graphite fluoride, tungsten carbide, talc, molybdenum disulfide (MoS), boron carbide and graphite. The boron nitride (BN), without limitation, may be hexagonal or cubic in orientation.
As explained above, the particulate matter imparts specific properties to the coating to be deposited. These properties may include one or more of wear resistance, reduced or increased friction, lubrication, phosphorescence, thermal conduction or insulation, and others, depending upon the specific particulate matter and its quantity utilized in the bath.
For example, for increased wear-resistance in the resultant coating, hard particulates, such as but not limited to diamond, carbides, oxides, and ceramics, may be included in the plating bath. Some examples of such carbides are silicon carbide, tungsten carbide, and boron carbide. An example of such an oxide is aluminum oxide. When particulate matter is incorporated into composite coatings for additional wear resistance, the particulate matter added is typically in the size range of 100 nanometers to 10 microns, and in the range of 10 to 40% by volume in the coating. The actual percent of particulate matter by volume depends on a number of factors including the particle size being incorporated.
For increased friction on the surface of a resultant coating, hard particulates, such as but not limited to diamond, carbides, oxides, and ceramics, may be included in the plating bath. Some examples of such carbides are silicon carbide, tungsten carbide, and boron carbide. An example of such an oxide is aluminum oxide. When particulate matter is incorporated into composite coatings for added friction, the particulate matter is typically greater than 10 microns in size and in the range of 25 to 50% by volume in the coating. 20 to 50 micron sized particles are common in composite electroless nickel coatings used for frictional properties. The actual percent of particulate matter by volume depends on a number of factors including the particle size being incorporated. Application of an overcoat of a conventional plated layer on top of the composite plated layer is also done in the field in order to further embed the particulate matter within the coating.
For increased lubrication or reduction in friction in the resultant coating, “lubricating particles,” such as polytetrafluoroethylene (PTFE), boron nitride (BN), talc, molybdenum disulfide (MoS), graphite or graphite fluoride may be included in the plating bath. These lubricating particles may embody a low coefficient of friction, dry lubrication, improved release properties, and repellency of contaminants such as water and oil. When particulate matter is incorporated into composite coatings for lubricity or reduction of friction, the particulate matter added is typically in the range of 10 to 30% by volume. The actual percent of particulate matter by volume depends on a number of factors including the type and particle size being incorporated. PTFE particles are typically less than 1 micron in size, and commonly 0.2 microns. Boron nitride and other particles incorporated for lubricity and low friction are typically 0.5 to 5 microns in size.
For light emitting properties in the resultant coating, particulates with phosphorescent properties such as, but not limited, to calcium tungstate may be included in the plating bath, When particulate matter is incorporated into composite coatings for light emitting properties, the particulate matter is typically in the range of 10 to 30% by volume. The actual percent of particulate matter by volume depends on a number of factors including the particle size being incorporated, and degree of phosphorescence of the particulate matter and degree of phosphorescence desired from the coating. Particles incorporated for light emitting properties are typically 0.5 to 5 microns in size.
For identification, authentication, and tracking properties in the resultant coating, various particulate and solid materials may be included in the plating bath so they will be incorporated into the coating and detectable either visually, under magnified viewing, or detection with a suitable detector. When particulate matter is incorporated into composite coatings for these properties, the particulate matter is typically in the range of 1 to 10% by volume. The actual percent of particulate matter by volume depends on a number of factors including the particle size being incorporated, and degree of visibility or detectability.
The inclusion of insoluble particulate matter in composite electroless baths introduces additional instability. To overcome the extra instability due to the addition of insoluble particulate matter to the bath, as described in U.S. Pat. No. 6,306,466, the general use of particulate matter stabilizers (PMSs) is believed to isolate the finely divided particulate matter, thereby maintaining the particular matter's “inertness”. Also, particulate matter stabilizers tend to modify the charge on the particulate matter to further maintain inertness. Altogether, by a precise addition and type of particulate matter stabilizers one may overcome the instability issues directly related to the addition of insoluble particulate matter to the plating baths, as shown in U.S. Pat. Nos. 4,997,686, 5,145,517, 5,300,330, 5,863,616 and 6,306,466.
Any known PMS may be used in the composite electroless bath in the present invention so long as its incorporation does not affect the basic kinetics of the plating process. Such PMSs are well-known, and include, without limitation, sodium salts of polymerized alkyl naphthalene sulfonic acids, disodium mono ester succinate (anionic and nonionic groups), fluorinated alkyl polyoxyethylene ethanols, tallow trimethyl ammonium chloride, and any of the PMSs disclosed in U.S. Pat. No. 6,306,466, which is incorporated herein by reference.
The electroless metallizing bath may also contain one or more complexing agents. A complexing agent acts as a buffer for reasons which may include pH control and maintaining control over the “free” metal salt ions in the solution, all of which aids in sustaining a proper balance in the bath solution. Some of these complexing agents are without limitation, lactic, malic, succinic, hydroxyacetic, acetic, and citric acids, ammonium compounds,and others.
The electroless metallizing bath may further contain a pH adjuster to also help control pH levels in the bath. Suitable pH adjusters include, without limitation, carbonates, hydroxides, acids which buffer at a desired pH range.
Historically electroless nickel and composite electroless plating processes have included heavy and/or toxic metals in the plating bath to overcome the inherent instability of the plating bath. Lead has been the most commonly used material to serve this purpose. Cadmium has also been used widely over the years as a brightener for electroless nickel coatings. But this incorporation of heavy metals into the plating baths presents multiple challenges. The heavy metals must be added in a sufficient amount to prevent the decomposition of the plating bath, but an increased concentration beyond the necessary level required to prevent the decomposition results in cessation or reduction of the plating rate. Increasingly stringent rules and regulations that restrict or prohibit the use of heavy metals, such as the Removal of Hazardous Substances (RoHS) and End-Of-Life Vehicle (ELV) Regulations, However, U.S. Pat. Nos. 7,744,685 and 8,147,601 disclose stable composite electroless nickel plating baths without the use of heavy and/or toxic metals. These patents are included herein by reference.
The electroless nickel and composite electroless nickel coatings of the present invention may contain heavy metals or may be essentially free of heavy metals, which means that no such heavy metal is added to the plating bath and/or the heavy metal concentration should be no more than a level that would cause the coating on articles plated in said bath to have a heavy metal concentration in excess of any relevant regulations.
In addition, in recent years, health and environmental concerns have been raised about the inclusion of certain materials such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), that may be used in composite plating systems, including those with PTFE. In particular, some of these materials included in the plating process later migrate from the plated objects into or onto other items, including humans and animals. For example, PTFE is used in plating cookware and, at times, small quantities of the plating material, including PTFE and any materials in the PTFE plating may be absorbed by the foods prepared in the cookware. Another example is in components used in consumer and industrial products such as automotives, electronics, and others which may ultimately be disposed and the disposition may lead to exposure or transfer of the PFOA or PFOS into the environment.
According to the United States Environmental Protection Agency (EPA), “Perfluorooctanoic acid (PFOA), also known as “C8” is a synthetic chemical that does not occur naturally in the environment. It has special properties that have many important manufacturing and industrial applications. The EPA has been investigating PFOA because PFOA is very persistent in the environment, is found at very low levels both in the environment and in the blood of the general U.S. population, remains in people for a very long time, and causes developmental and other adverse effects in laboratory animals. Major pathways that enable PFOA, in very small quantities, to get into human blood are not yet fully understood. PFOA is used to make fluoropolymers and can also be released by the transformation of some fluorinated telomers. However, consumer products made with fluoropolymers and fluorinated telomers, including Teflon® and other products, are not PFOA. Rather, some of them may contain trace amounts of PFOA and other related perfluorinated chemicals as impurities. The information that the EPA has available does not indicate that the routine use of consumer products poses a concern. At present, there are no steps that EPA recommends that consumers take to reduce exposures to PFOA. In 2006, EPA and the eight major companies in the industry launched the 2010/15 PFOA Stewardship Program, in which companies committed to reduce global facility emissions and product content of PFOA and related chemicals by 95 percent by 2010, and to work toward eliminating emissions and product content by 2015.”
In addition, the United States Environmental Protection Agency states that, “In January 2005, the EPA Office of Pollution Prevention and Toxics submitted a Draft Risk Assessment of the Potential Human Health Effects Associated With Exposure to Perfluorooctanoic Acid and Its Salts (PFOA) to the EPA Science Advisory Board (SAB) for formal peer review. EPA sought this early stage scientific peer review from an outside panel of experts in order to ensure the most rigorous science is used in the Agency's ongoing evaluation of PFOA. That draft was preliminary and did not provide conclusions regarding potential levels of concern. The SAB reviewed the information that was available at the time, and suggested that the PFOA cancer data are consistent with the EPA Guidelines for Carcinogen Risk Assessment descriptor “likely to be carcinogenic to humans.”
Regarding PFOS, The Organization for Economic Cooperation and Development has stated that “Sufficient information exists to address hazard classification for all SIDS [Screening Information Data Set] human health endpoints. PFOS is persistent, bioaccumulative and toxic to mammalian species. There are species differences in the elimination half-life of PFOS: the half-life is 100 days in rats, 200 days in monkeys, and years in humans. The toxicity profile of PFOS is similar among rats and monkeys. Repeated exposure results in hepatotoxicity and mortality; the dose-response curve is very steep for mortality. This occurs in animals of all ages, although the neonate may be more sensitive. In addition, a 2-year bioassay in rats has shown that exposure to PFOS results in hepatocellular adenomas and thyroid follicular cell adenomas; the hepatocellular adenomas do not appear to be related to peroxisome proliferation. Further work to elucidate the species differences in toxicokinetics and in the mode of action of PFOS will increase our ability to predict risk to humans. Epidemiologic studies have shown an association of PFOS exposure and the incidence of bladder cancer; further work is needed to understand this association. Sufficient information exists to address hazard classification for all SIDS environmental endpoints. PFOS is persistent in the environment and has been shown to bioconcentrate in fish. It has been detected in a number of species of wildlife, including marine mammals. Its persistence, presence in the environment and bioaccumulation potential indicate cause for concern. It appears to be of low to moderate toxicity to aquatic organisms but there is evidence of high acute toxicity to honey bees. No information is available on effects on soil- and sediment-dwelling organisms and the equilibrium partitioning method may not be suitable for predicting PNECs [Predicted No Effect Concentrations] for these compartments. PFOS has been detected in sediment downstream of a production site and in effluents and sludge from sewage treatment plants.”
The EPA is also actively investigating the levels of contamination of PFOS in the environment from the land to water supplies, animals, animal products such as milk, and its effect on animal and human health.
The present invention therefore includes compositions, baths, and methods for composite plating that contain PFOA and/or PFOS, or may be free or have only trace amounts of PFOA and/or PFOS.
Once the bath has been prepared, it is ready for use in the electroless plating process of the present invention. This involves contacting the surface of an article with the electroless metallizing bath. However, the article to be coated may require preliminary preparation prior to this contact. This preparation includes the removal of surface contaminants. For example, this process may involve any of, but not limited to, degreasing, alkaline cleaning, electrocleaning, water or solvent rinsing, acid activation, pickling, ultrasonic cleaning, physical modification of the surface, vapor or spray treatments, etc.
The mechanism by which a coating is formed on an article in composite electroless plating is well-known in the art. For example, U.S. Pat. No. 4,830,889, which is incorporated herein by reference, describes the electroless reaction mechanism. Generally, metal ions are reduced to metal by action of chemical reducing agents, which are electron donors. The metal ions are electron acceptors which react with the electron donors. The article to be coated itself may act as a catalyst for the reaction. The reduction reaction results in the deposition of a coating with the metal (or electroless metal) onto the surface of the article.
The article to be coated may be any substrate or material capable of being coated through composite electroless plating. Some examples of such articles are components in high wear, abrasive, impact, cutting, grinding, pumping, material transfer, molding, frictional, and sliding applications.
The coating of textile machinery parts has been a commercially accepted practice, especially when applied to open-end (OE) and ring spinning operations. For example, combing tolls and rotor cups have been coated with composites bearing wear resistance particles such as diamond and silicon carbide particles. Rotor shafts used for open-end spinning have been coated primarily with a composite bearing silicon carbide. Similarly, rings and travelers used in ring spinning have been used with a variety of composites and other coatings. While it is well documented that the use of composite coatings bearing wear resistance particles extends the lifetime of machinery parts, their use creates certain potential problems as to the degradation of the physical properties of the yarn when contacted with the wear resistant coated machinery part. Accordingly, the present invention includes textile manufacturing machine parts with an improved composite coating that is compatible with and provides improved results on the manufacture of certain textile materials. This criticality is becoming more pronounced as new man made fibers are developed and as the speed for the associated spinning parts is increased. The use of such coatings will provide a coated machinery part improved results relative to the yarn and the finish upon such yarns.
Composite electroless nickel coatings with diamond particles have been used significantly is the textile industry for roughly 30 years. One component used in this industry in the combing roll. Due to the abrasiveness of the contacting textile material, increased wear resistance is desired for these components. Combing rolls are used with many varieties of textile materials including natural and man-made fibers. The abrasiveness to the combing rolls varies depending on the variety of the fiber used and the grade of cleanliness of the fibers, as well as the type and speed of the combing roll, and other factors. One well established measure to combat the abrasive wear of the fibers to the combing rolls is to coat some or all portions of the combing rolls (at least the teeth portion) with a wear resistant coating. Electroless nickel composite coatings with diamond particles are the most widely used coatings for this purpose. The most common specification for this coating is to apply a coating about 20-30 microns thick containing about 20-40% by volume of about 2.0 micron average size diamond particles into the coating. The coating may then be over-coated with a thinner layer of electroless nickel, and is then generally heat-treated to increase the hardness and adhesion of the coating.
The overcoat generally replicates the surface profile of the underlying composite layer, but since the overcoat is somewhat softer than the composite layer, the surface will be able to smooth out easier and sooner when the combing roll is in use than would be the case of the composite layer alone. This is often referred to as the “break-in” period, and it is desirable for the break-in period to be as brief as possible to maximize efficiency and economy of the textile production process as it relates to time, materials, energy, etc.
The invention related to over-coating composite electroless nickel coatings with a conventional electroless nickel coating for textile machinery parts is disclosed in U.S. Pat. No. 4,358,922, and is included herein by reference.
As is well known in the field of textile manufacturing and as can be seen on the surface of the traditional composite electroless nickel coatings used in this field, these traditional coatings, even those with an overcoat free of particles, may be too rough for an acceptable break-in period and/or effective use in processing certain types of fibers. The problem with such roughness on the surface of textile machine parts is that this roughness can destroy small fibers not fully attached to the shaft of the yarn. This creates dust in the processing of the fibers that can accumulate in the groove of a rotor cup used in rotor spinning applications and other areas of the spinning apparatus. The accumulation of dust in this groove can lower yarn quality and cause yarn breaks, thereby adding time and expense to the textile preparation process.
These factors are especially relevant with polyester and various man-made fibers. An informative text on this matter was presented at the 44th annual Technical Conference of the Society of Vacuum Coaters in April 2001 in Philadelphia, Pa. This text focuses on the processing of polyester fibers, and concurs that combing rolls used in open end spinning face substantial wear and require additional measures of wear resistant. Further, this text concurs that the traditional composite electroless nickel-diamond coating is too rough for the sensitive polyester fibers. The text, therefore, presents an alternative physical vapor deposition coating to add wear resistance without creating a part surface that is too rough for the sensitive polyester fibers. This text does not envision the possibility of modifying the surface of the traditional composite electroless nickel-diamond coating and/or replacing the two micron diamond particles of the traditional composite coating with the smaller hard particles, nor does it envision a subsequent “blackening” finishing process as disclosed in the present invention onto the surface of the composite electroless plated article. Similarly, suppliers of such combing rolls to the open end textile industry have developed other surface treatments designed to increase wear life of these critical parts while maintaining a surface profile compatible with various delicate textile materials. None of these methods, however, include the utility and novelty of the present invention. Moreover, these other methods suffer from various drawbacks, including high cost of manufacture and incompatibility with the substrate. Many coating or surface techniques that may be attractive in theory are not able to adhere to or replicate the complex geometry of parts that are the subject of this invention such as combing rolls, rings, travelers, rotors, and rotor shaft.
Aside from these more recent developments, users of these textile parts have used uncoated combing rolls or combing rolls coated with only a layer of conventional electroless nickel devoid of any particulate matter. The electroless nickel alone provides some added wear resistance and does not generate roughness on the surface. The added wear life provided by electroless nickel alone is less than commercially desirable for production and economic concerns.
More frequent replacement of worn components means additional cost for the replacement parts, and is a cost of time, labor, and lost productivity to accomplish the replacing of worn with new parts. Moreover, the quality of the textile product produced by the spinning parts will then not be consistent throughout the operating lifetime of the spinning parts. The initial quality produced by a new spinning part during the break-in period is often of lower quality until the part has been used for a sufficient period during which the part's surface is essentially polished. Once the part is sufficiently worn, the quality of the product again degrades. Therefore, the longer the main lifetime of the part can be prolonged will result in an extended period of producing a product of higher and more consistent quality. The coated parts associated with the present invention should provide consistent production quality sooner, and an extended period of consistent and quality product.
In order to facilitate the consistent production quality desired of textile machine parts, such coated parts may undergo surface finishing treatments, such as mechanical finishing, to smooth the surface of the coated part. In some instances the need such surface finishing may be reduced or avoided by the alteration of the surface of the coating by a blackening treatment as described in this present invention.
The technique of blackening electroless nickel coatings is known in the industry. A number of methods have been developed to produce black electroless nickel, including heating the coating in a non-inert atmosphere to oxidize the phosphorous in the electroless nickel coating into a bluish-purple/black color. Another method involves adding materials to the electroless nickel plating bath similar to what can be used in black electrolytic nickel plating baths. Another method is to use certain metal containing solutions that will alter the color of the electroless nickel coating from yellow golden tones to blue and shades of black that are neither as uniform nor distinct as other methods of blackening.
The most common process is generally characterized by the oxidation or etching of an electroless nickel coating. This process causes a fine alteration (roughening, pitting, etc.) of the surface of the electroless nickel such that the surface absorbs rather than reflects light, thereby giving the surface a black appearance. The process can be varied by the alloy and composition of the electroless nickel coating, the composition of the oxidizing solution, the concentration of the oxidizing solution, the time and temperature of the oxidizing solution during use, the agitation used during the oxidization process, and other factors. Oxidizing materials that can be used include acids, metal chlorides, peroxides and other oxidizing agents. Acids that can be used include nitric, sulfuric, hydrochloric, and others. Additional materials may be used in conjunction with one or more of the oxidizing agents to enhance, stabilize, or otherwise improve the efficacy of the oxidation of the coating, the reactivity of the solution, and/or the health, environmental or safety of the oxidization process. Such additional materials may include, without limitation, potassium permanganate, ferric chloride, copper chloride, nickel chloride,
Additional information on the technique of blackening electroless nickel can be found in U.S. Pat. No. 4,361,630 which is included herein by reference, and the article entitled Investigation of the Blackening Process of Electroless Nickel-Phosphorous Coatings and Their Properties, by D. Beckett, Y. Liu, and a Hawthorne, posted on: Jan. 31, 2011 on line at: http://www.pfonline.com/articles/investigation-of-the-blackening-process-of-electroless-nickel-phosphorous-coatings-and-their-properties
It is an object of the present invention to improve significantly the performance of open-end and ring spinning textile machinery parts and other articles used in the textile and other industries and applications, and to eliminate many of the disadvantages associated with prior art coatings.
It is an object of the present invention to provide composite electroless coatings with improved surface profile with advantages for molding and texturing applications.
It is an object of the present invention to provide composite electroless coatings with improved surface profile with advantages for frictional, wear, thermal, light absorption, aesthetic, and other properties.
These and other objects of the present invention together with the advantages over the existing prior art and method will become apparent from the following specification and the method described herein.
The present invention is directed processes and product related to blackened coatings, blackened electroless nickel coatings, blackened electroless nickel coatings including particulate matter, coatings with cover coats, coatings with voids, and the methods of application and products with such coatings. The appearance of a blackened coating, including blackened composite electroless nickel coatings, may range from a dark gray to black color. The actual color will depend on the many factors disclosed in the present invention such as coating composition, blackening process, and geometry of the article with the blackened coating.
Examples of parts which benefit from the coatings of the present invention include various open end spinning parts such as combing rolls, rotor cups, shafts, housings, and removal blades, and other parts in other types of textile manufacturing, and their surface plating, where controlled surface characteristics are necessary. Ring spinning applications with rings, travelers and other parts are such examples. Other such applications include ones that utilize similar teeth as combing rolls such as carding flats and other applications.
This invention is further envisioned to make such coatings feasible and provide similar performance advantages in non-textile applications that have other materials that are also sensitive to the surface of the coated objects.
Although a primary application is textile parts, other applications include firearms as well as other objects in which plating is beneficial.
The coating processes of the present invention involved some or all of the following steps. An aqueous bath for electroless nickel (or other form) of plating is prepared using some combination of plating materials, particular matter, and other materials as described herein. In the preferred embodiment, the plating bath of the present invention includes a metal salt, reducing agent, particulate matter, a particulate matter stabilizer, etc. etc. The concentrations of the various elements may vary. The bath is controlled for at least temperature and/or pH. An object for plating, initially prepared such as by cleaning, is placed in the bath for some period of time with the result being a coating on the surface of the object. The object may then be blackened, such as by oxidation. The object may also be placed in more than one plating bath with the result being coated with two or more coatings where the second plating bath, may differ from the first plating bath, for the purpose of providing the object with two or more composite electroless coatings and/or one or more composite electroless coatings plus one or more electroless coatings. An electroless coating may be applied as a cover coat and such processes may be repeated. The process may further include surface finishing, such as by blasting, tumbling, polishing or other means described herein.
In describing the preferred embodiments of the present invention, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and is to be understood that each specific term includes all technical equivalence which operate in a similar manner to accomplish a similar purpose.
In the preferred embodiment of the present invention, and as detailed in the examples, a plating bath is formed and an article is plated by placing it in the bath. The bath is operated at an elevated temperature, and includes diamond particulate matter and a particulate matter stabilizer. Once plated, the article is moved to an oxidizing bath, which results in the plated material turning darker in color, thereby losing its reflectability.
According to the concept of the present invention, the composite electroless coatings or combinations of coatings with and/or without particles are applied onto parts. For example, such parts include parts with a single composite electroless nickel coating; parts coated with a composite electroless nickel coating followed by an overcoat of an electroless nickel coating, parts coated with an electroless nickel coating followed by a composite electroless nickel coating; parts coated with multiple layers of composite electroless nickel coatings, and parts with other combination variations.
The parts coated with such coatings may be treated with a blackening process to alter the surface of the coated part. The unique composition of composite electroless coatings with co-deposited particulate matter, in comparison to similar coatings devoid of co-deposited particulate matter, provides a challenge for the most efficient, effective, and/or optimal blacking of the surface. As the presence of particulate matter within composite electroless coatings and on the surface of such coatings affects the appearance of these coatings, so too do such particles affect the ability of such coatings to be blackened by the more conventional methods in the field for conventional electroless coatings. The particulate matter that protrudes from the surface of composite coatings affects the appearance of the coating in at least two primary ways; 1) the protruding particulate matter has a color which is typically different from the color of the metal matrix of the coating and therefore the appearance of the coating is a composite of both the metal matrix and the protruding particulate matter, and 2) the protruding particulate matter affects the surface profile by generally making the surface rougher, and therefore the presence of particulate matter within a coating affects the reflectivity of light coming from the surface of said coatings. The presence of particulate matter within a coating also affects the blackening of the coating. The reason for this phenomena is that because this particulate matter comprises some portion of the total coating composition, the amount of metal matrix in a coating is reduced by the amount of particulate matter included in the coating and most specifically depending on how much of the particulate matter is contained on the surface of the coating. The percent of particulate matter in most commercially used composite coatings is in the range of ten to fifty percent by volume. The method of blackening the coating in the present invention is accomplished by oxidizing the metal matrix of the coating, thereby changing the chemical makeup of the coating without affecting the particulate matter embedded in the coating. The particulate matter itself will generally not be altered by the oxidizing solution. Therefore the amount of metal matrix available for blackening in a composite coating is less than the amount of metal matrix available in a similar coating devoid of particulate matter. This is the nature of the challenge in producing effective and desirable degrees of blackening of the surfaces of composite coatings.
One method of the present invention that overcomes the unique challenge of blackening composite coatings is the performance of the blackening process in an ultrasonic medium. Specifically, the process can be implemented in a container where the coated article is immersed in a blackening solution for a period of time during which ultrasound waves are introduced to the solution for some or all of the time during which the articles are immersed in the solution. The blackening, or oxidizing solution, is typically an aqueous solution comprising an acid and/or other oxidizing agents, oxygenation reagents, metal halides, peroxides, surfactants, any metal compounds that may aid in the oxidization or blackening of the composite coating at a specific pH and temperature range. This solution is controlled by analysis of each component by wet chemical analysis, physical analysis, and/or instrumental analysis.
Employing ultrasonic forces to the oxidizing solution in which a composite electroless coated article is being blackened promotes the liberation of particulate matter that is either loosely clinging to the surface of said article and/or lightly entrapped in the coating. As most particulate matter is not black, but rather particulate matter including diamond, silicon carbide, aluminum oxide, tungsten carbide, boron nitride, PTFE, and others are white or gray in appearance, often light gray, the presence on the particulate matter on the surface of a coated article will reduce the degree of blackness that is produced by the oxidation of the coated article. It is also believed that the use of ultrasonic energy accelerates the oxidation of the composite electroless coating. The use of ultrasonic energy can also be effective in the rinsing and/or cleaning of composite coatings before and/or after coated articles are immersed in a blackening solution, as this also contributes to the liberation of particulate matter on the surface of the coating which can affect and limit the potential for a composite coating to be blackened. The ultrasonic energy is typically added to a solution by transducers. The transducers are either placed in a container containing the operating solution or in a larger container containing a liquid such as water or a solution. In that case, a smaller container, in which the article is immersed, is immersed in the larger container. The operating solution is meant to refer to either a blackening solution or a rinsing or cleaning solution that may be used within the blackening process. The amount of ultrasonic energy used, typically rated in watts and applied at one or more frequencies (in kilohertz (kHz)), which can be of any amount effective to produce the desired results. The amount will differ and depend on the type, concentration, temperature, pH, age, and other factors of the blackening and/or rinsing or cleaning solutions, as well as the composition and condition of the coating on the article being immersed, and the volume of the parts and solution(s). Similarly, the duration that the charge is applied may vary. The longer the duration, the more oxidation and, therefore, the darker the resultant coating.
An alternative method of providing a black composite electroless nickel coating in the present invention is the metallization of parts in a plating bath with particulate matter whereby the resulting coating exhibits a unique structure with a plurality of holes in the coating. Such holes absorb light and therefore provide a black appearance of the coated parts. Such holes further provide a lower frictional surface. Such holes further provide an ability of the coating to retain additional materials which may be advantageous when the part is used for its intended purpose. For example, a part coated with this variation of a black composite electroless nickel coating that is used in an application also utilizing one or more lubricants can retain such lubricants within the holes of the coating to yield further lubricity to the part during use. Another example is that such a part, when used in the textile industry, for example, could retain textile fibers, or dust, that will then protect the part from wearing at a rate as fast as a similar part without this coating variation of the present invention. It is believed that the composition of the plating bath, primarily the inclusion of certain particulate matter stabilizers, causes a unique stabilization of the plating bath on the surface of the articles being coated and thereby result in the unique formation of holes in the coating. While not wanting to be bound by theory, it is believed that the particulate matter stabilizers affect the formation of hydrogen bubbles during the plating process in a way in which they cling longer to the surface of the surface and thereby inhibit the deposition of the metal matrix in the areas occupied by such bubbles.
Examples of parts of the present invention include open-end spinning machinery parts (rotors, combing rolls, navels, spinning rings, travelers, and others). Preparation of these parts according to the present invention will yield a unique surface that will result in a faster break-in period of the coated part. This friendlier contact between the yarn and the coated machinery parts thereby minimizes any damage(s) to the yarns and resulting in improved physical properties for the processed yarn, and economy of use in such coated machinery parts. The oxidization of the coating causes light etching of the surface of the coating. In the oxidization process, the surface of the coating becomes essentially pitted or slightly roughened. These newly formed peaks caused by the blackening process are then easier to be smoothed off by mating materials such as textile materials. This effect is analogous to the greater ease of wearing down a sheet of ice that has been pitted by an application of salt crystals in comparison to the more difficult task of wearing down a solid smooth sheet of ice.
Alteration of the more traditional surface of the coated textile machinery part, or other parts for other applications, can allow for the avoidance of other surface treatments that have traditionally been required to prepare a coated part for use. For example, the blackening of parts used in textile manufacturing can allow the avoidance of mechanical finishing operations such as blasting, polishing, tumbling and other processes that are commonly used, time consuming, and less consistent than the chemical blackening treatment. In the case of physical mechanical finishing, these processes are generally much less consistent than chemical treatments because these processes are often done by hand, individually, or in small batches.
Another example of parts of the present invention is parts useful in firearm devices. Firearms are complex devices with numerous components. Different of these components require a variety of surface properties such as corrosion resistance, wear resistance, high or low friction, heat transfer, thermal insulation, and others. Many of these properties can be provided through the use of composite electroless coatings. However, many of these components further require the appearance of the component to be black. The need for blackness or low reflectivity is very important as firearms are often produced and intended to be discreet, not reflect light, and aesthetically pleasing to the consumer of such products. Therefore the present invention serves this unresolved limitation of prior technologies to provide both the mechanical properties required for firearm component surfaces as well as the black appearance that is needed.
Though the present invention primarily focuses upon diamond as the particulate matter to be used in the composite coatings for the specific textile machinery parts, other particles fall within the spirit of this invention. Other examples include, but are not limited to, silicon carbide, boron carbide, aluminum oxide, tungsten carbide and other hard particles fall within the spirit of this invention. In at least some circumstances, one or more particulate matter stabilizers may be include in the bath, and the selection may vary by the particulate matter used.
In addition, the bath may be further comprised of a lubricating material, which would be included in the coating material resulting on the article.
In one embodiment of the present invention the plating composition includes particulate matter with characteristics of lubrication, release, or low friction properties and such matter is included within the coating containing wear resistant particulate matter for additional performance benefits. Such particulate matter may include, as examples, PTFE, other fluoropolymers, boron nitride, graphite, graphite fluoride, molybdenum disulfide, talc, and others.
In another embodiment of the present invention two or more types of particulate matter are included in the plating composition in order to provide multiple properties within the same coating. Such properties may include, but are not limited to wear resistance, hardness, friction, low friction, release, lubricity, identification, authentication, and others.
As is common in the field of coating articles with composite plated coatings, a post-plating heat treatment of at least 200 degrees Celsius may be included within the scope of this invention. Electraless nickel phosphorous coatings, for example, commonly are heat treated to a temperature of about 350 to 400 degrees Celsius for one or more hours to achieve maximum hardness of the metal matrix.
The present invention encompasses all varieties of electroless nickel coatings with varying concentrations or freedom from various materials such as, but not limited to, lead, cadmium, heavy metals, toxic metals, PFOA, PFOS and others that are subject of environmental and related regulations such as Restriction of Hazardous Substance Directive (RoHS), Directive on Waste Electrical and Electronic Equipment (WEEE), End of Life Vehicle Directive (ELV), and the like.
The present invention further includes any and all post-coating subsequent finishing operations that can achieve the polishing and/or surface modification necessary to produce a surface compatible with the uses of the articles described herein. Certain examples include, but are not limited to rinsing, oxidizing, etching, polishing, sanding, grinding, honing, abrasive blasting, blasting with spherical or generally spherical materials, tumbling, electro polishing, and deburring.
While the novel treatment disclosed in this invention may initially make the surface rougher, the micro roughness peaks may in actuality be easier for the coating to be subsequently smoothed by break-in, use, or by other means of finishing.
The unique surface of coatings with the treatments as disclosed in this invention will also provide unique and previously unforeseen properties. As the composite coatings with diamond are treated with an oxidizing or otherwise blackening process, more of the co-deposited diamond particles become exposed on the surface. As diamond is an outstanding conductor of heat, the increased exposure of diamond on the surface of an article coated with a composite coating containing diamond should enhance the heat transfer properties of such coatings, a property that is known in the industry. Other materials are also known to enhance heat transfer and can be incorporated into composite coatings. Silicon carbide is one such example. Conversely, articles with composite coatings containing particles that have thermal insulation properties may be similarly enhanced to have greater thermal insulation properties if the coating on such articles are treated in a blackening solution as disclosed in the present invention and therefore have more of such particles exposed on the surface of the coating compared to similar articles without the alteration of the surface provided for by a blackening process. Certain materials, most notably, certain ceramics and polymers, are well known to be insulators to thermal transfer.
The altered color caused by the blackening treatment also has uses for articles where identification or authentication properties are desired. That is, the distribution of particulates and the presence of voids, either alone or in combination, can be used to form an effective signature for the plating or the article, and such a signature is later usable to uniquely identify or authenticate a plated article. The black color alone can also distinguish a composite coated article from a composite coated article that has not been blackened in an oxidizing solution and is in its as-plated appearance. For identification purposes, an article may be photographed in some way, such as by scanning electron microscope and computer algorithms may be applied to the photograph(s) to identify a particular signature. Later photographs can be used for comparative purposes for validating the signature.
The micro pitted/roughened surface as demonstrated in the examples and photographs above also provides an opportunity for materials such as lubricants, release compounds, and others to be trapped, retained, etc. in the surface and thereby improve the performance of articles where these properties are desired.
Although the examples detailed below depict specific combinations of elements, time, and control, the reader should recognize that the present invention is not limited to the specific materials and metrics in the examples. More generally, the plating materials can include any of nickel, phosphorous, boron, cobalt, tungsten, copper, zinc, chrome, and others. The pH can vary by application but is preferably in a range of 4.0 to 8.0. The bath temperatures can preferably be in the range of 20 to 100 degrees Celsius. The duration of the plating time is preferably in the range of 15 to 600 minutes.
The following example is an illustration whereby diamond particles were codeposited in a hard metallic matrix. It should be noted that the present invention is not limited to the type of bath used herein, but in general for electroless deposits of the various metals and alloys. Moreover, the invention is not limited to the specific particles used, or method of altering the surface of the coating.
In the current example an electroless nickel plating bath, NiPlate 830 sold by Surface Technology, Inc, of Trenton, N.J., was used to provide a Ni—P type alloy with diamond particles also known as “CDC-2”. The bath was operated at a pH of 6.3 and a temperature of about 170 degrees F. Six steel panels after normal cleaning and activation were plated for 65 minutes under the above conditions. A cross sectional inspection of the coating on one of the panels revealed a significant quantity of codeposited diamond particles. Three of these coated panels were then treated by immersion in an oxidizing solution which caused a distinct change in the appearance of the coating surface to a black color from the light gray color of the untreated coated panels. The oxidizing solution of the present example was an aqueous solution of sulfuric acid and potassium permanganate, with a pH of less than 1 used at a temperature of 20 degrees Celsius for an immersion time of 105 seconds.
The following are SEM photographs of the surface of the as plated CDC-2 panels and the surface of panels from the same coating after the “black” treatment, These SEM photographs at 200× magnification show the surface texture effect of the oxidization treatment.
In the current example an electroless nickel plating bath, NiPlate 830 sold by Surface Technology, Inc., was used to provide a Ni—P type alloy with diamond particles, also known as CDC-2. The bath was operated at a pH of 6.3 and a temperature of 168 degrees F. Six steel panels after normal cleaning and activation were plated for 65 minutes under the above conditions. The coated panels were then plated with an “overcoat” of an electroless nickel coating that was approximately 2-7 microns thick and essentially free of particles. This overcoat was applied in an electroless nickel bath, NiPlate 100 sold by Surface Technology, mc, to provide a medium phosphorous Ni—P type alloy. The bath was operated at a pH of 4.8 and a temperature of 188 degrees F., and a cycle time of 12 minutes. The coated panels therefore were coated with a coating known as CDC-2/N. A cross sectional inspection of the coating on one of the panels revealed a significant quantity of codeposited diamond particles in the first layer and essentially no particles in the overcoat layer. Three of these coated panels were then treated by immersion in an oxidizing solution which caused a distinct change in the appearance of the coating surface to a black color from the shiny nickel color of the untreated coated panels. The oxidizing solution of the present example was an aqueous solution of sulfuric acid and ferric chloride, with a pH of less than 1 used at a temperature of 20 degrees Celsius for an immersion time of 75 seconds.
The following are SEM photographs of the surface of the as plated CDC-2/N panels and the surface of panels from the same coating after the “black” treatment. These SEM photographs at 1,000× magnification show the surface texture effect of the oxidization treatment.
The following example is an illustration whereby boron nitride particles were codeposited in a hard metallic matrix. It should be noted that the present invention is not limited to the type of bath used herein, but in general for electroless deposits of the various metals and alloys. Moreover, the invention is not limited to the specific particles used, or method of altering the surface of the coating.
In the current example an electroless nickel plating bath, NiSlip 25 sold by Surface Technology, Inc., was used to provide a Ni—P type alloy with boron nitride particles. These particles had a mean particle size of about one micron. The bath was operated at a pH of 6.3 and a temperature of about 170 degrees F. Six steel panels after normal cleaning and activation were plated for 65 minutes under the above conditions. A cross sectional inspection of the coating on one of the panels revealed a quantity of about 10 to 15% codeposited boron nitride particles. Three of these coated panels were then treated by immersion in an oxidizing solution which caused a distinct change in the appearance of the coating surface to a black color from the matte nickel color of the untreated coated panels. The oxidizing solution of the present example was an aqueous solution of sulfuric acid and potassium permanganate, with a pH of less than 1 used at a temperature of 20 degrees Celsius for an immersion time of 40 seconds.
The following are SEM photographs of the surface of the as plated NiSlip 25 panels and the surface of panels from the same coating after the “black” treatment. These SEM photographs at 200× magnification show the surface texture effect of the oxidization treatment.
Coefficient of friction testing on two panels of the present example was then implemented in accordance with ASTM G133-05 (2010) Procedure A with parameters including: 0.505 N applied normal force, 5mm stroke length, 0.05 m sliding distance, 0.001 m/s maximum linear speed, 0.06 s−1 frequency of oscillation, 5 cycles, 10 mm ball diameter, SS440C grade 25 ball material, no lubricant, air atmosphere, ambient temperature. Testing was done on the two of the panels plated according to the above condition, whereby one panel was tested in its as-plated condition and the second panel was tested after the immersion in the oxidizing solution described above which caused the appearance of the coating surface to be dark gray to black in color. The results of this coefficient of friction testing were an average of 0.349μ+/−0.012 for the panel with the as-plated coating, and 0.351μ+/−0.023 for the panel that was coated and blackened as above. It was unforeseen that despite the alteration to the surface finish caused by the blackening treatment, visible in the SEM photographs in this disclosure, that the coefficient of friction results between the as-plated panel and the blackened panel would be virtually identical, at least for this variation of a composite coating of a low phosphorous alloy of nickel and phosphorous and approximately 10 to 15% boron nitride particles by volume.
The following example is an illustration whereby PTFE particles were codeposited in a hard metallic matrix. It should be noted that the present invention is not limited to the type of bath used herein, but in general for electroless deposits of the various metals and alloys. Moreover, the invention is not limited to the specific particles used, or method of altering the surface of the coating.
In the current example an electroless nickel plating bath, NiSlip 515 sold by Surface Technology, Inc., was used to provide a Ni—P type alloy with PTFE particles that is essentially free of PFOA and PFOS. The Ni—P alloy of this plating confirms to RoHS, ELV, WEEE and similar regulations. The bath was operated at a pH of 6.1 and a temperature of about 192 degrees F., and a plating rate of about 0.0008 inches per hour. Three steel panels after normal cleaning and activation were plated for 30 minutes under the above conditions. A cross sectional inspection of the coating on one of the panels (panel 1) revealed a quantity of abut 20 to 25% codeposited PTFE particles by volume. The individual particle size of the PTFE was 0.2 microns, with some of these individual particles clustered into larger agglomerates within the composite coating. One of these coated panels (panel 2) were then treated by immersion in an oxidizing solution which caused a distinct change in the appearance of the coating surface to a dark gray/black color from the matte metallic color of the untreated coated panels. The oxidizing solution of the present example was an aqueous solution of ferric chloride, with a pH of less than 1 used at a temperature of 25 degrees Celsius for an immersion time of 90 seconds.
Panel 2 and panel 3 (a steel panel coated simultaneously with panels 1 and 2) were then tested for the coefficient of friction in accordance with ASTM G133-05 (2010) Procedure A with parameters including: 0.505 N applied normal force, 5mm stroke length, 0.05 m sliding distance, 0.001 m/s maximum linear speed, 0.06 s−1 frequency of oscillation, 5 cycles, 10 mm ball diameter, SS440C grade 25 ball material, no lubricant, air atmosphere, ambient temperature. Testing was done on the two of the panels plated according to the above condition, whereby one panel was tested in its as-plated condition and the second panel was tested after the immersion in the oxidizing solution described above which caused the appearance of the coating surface to a black color. The results of this coefficient of friction testing were an average of 0.074μ+/−0.006 for panel 3 with the as-plated coating, and 0.162μ+/−0.013 for panel 2 that was coated and blackened as above. It was unforeseen that the coefficient of friction results between the as-plated panel and the blackened panel would be significantly different in relation to the lack of difference in coefficient of friction between the as-plated and blackened panels with an electroless nickel-boron nitride composite coating in Example 3; at least for this variation of a composite coating of a medium phosphorous alloy of nickel and phosphorous and approximately 20 to 25% PTFE particles by volume.
The following example is an illustration whereby PTFE particles were codeposited in a hard metallic matrix. It should be noted that the present invention is not limited to the type of bath used herein, but in general for electroless deposits of the various metals and alloys. Moreover, the invention is not limited to the specific particles used, or method of altering the surface of the coating.
In the current example an electroless nickel plating bath was used to provide a Ni—B type alloy with PTFE particles. The bath was operated at a pH of 6.2 and a temperature of about 158 degrees F. The individual particle size of the PTFE was 0.2 microns, with some of these individual particles clustered into larger agglomerates within the composite coating. Four steel panels after normal cleaning and activation were plated for 60 minutes under the above conditions.
The following SEM and cross sectional photographs of the as plated panels demonstrate a unique structure with a multitude of holes in the coating. Such holes absorb light and therefore provide the black appearance of the coated parts that is visible to the unaided eye. The cross sectional photograph further demonstrates the incorporation of PTFE particles within the metal matrix.
For comparison, four other steel panels were given the same cleaning and activation and plated for 60 minutes at the above conditions with the exception that no PTFE dispersion was added to the Ni—B plating bath. The resulting plated panels had a matte metallic appearance to the eye and no multitude of holes in the coating as in the photographs below of the Ni—B—PTFE variation.
Example 5—SEM photograph of Ni—B—PTFE coating surface
Example 5—Cross Sectional photograph of Ni—B—PTFE coating
Two rotorcups useful in the open end spinning of textile products were coated simultaneously with a composite electroless nickel and diamond coating. The thickness of the coating was 20-30 microns. The average diamond particle size was 2 microns. The concentration of diamond particles in the coating was about 20 to 30 percent by volume. The two rotor cups were simultaneously heat treated to a temperature of 350 degrees Celsius. One of the two rotorcups was then immersed in a chemical solution to oxidize the surface of the coating and thereby cause it to become black in appearance. The oxidizing solution of the present example was an aqueous solution of sulfuric acid and potassium permanganate, with a pH of less than 1 used at a temperature of 20 degrees Celsius for an immersion time of 105 seconds.
Both rotorcups were then used in an open end spinning device to produce yarn, Analysis of the performance of these two rotorcups demonstrated that the blackening treatment caused no negative influence on the yarn's quality, but produced yarn with a higher yarn strength.
In the current example an electroless nickel plating bath, NiPlate 830 sold by Surface Technology, Inc., was used to provide a Ni-P type alloy with two micron sized diamond particles, also known as CDC-2. The bath was operated at a pH of 6.3 and a temperature of 168 degrees F. Two steel panels after normal cleaning and activation were plated for 70 minutes under the above conditions. A cross sectional inspection of the coating on one of the panels revealed about 25 to 30% of co-deposited diamond particles in the coating by volume. One of these coated panels was then treated by immersion in an oxidizing solution for 30 seconds which caused a distinct change in the appearance of the coating surface to a black color from the light gray color of the untreated coated panel. The second panel was then treated by immersion for 30 seconds in the same oxidizing solution as the first panel, but while this second panel was immersed in the oxidizing solution, ultrasonic energy was provided to the oxidizing solution at 500 Watts and a frequency of 40 kHz. The ultrasonic oxidization process caused a distinct change in the appearance of the coating surface to a black color from the light gray color of the untreated coated panel, and the degree of blackness of the panel oxidized in the presence of ultrasonic energy was visibly and distinctly greater, or blacker, than the degree of blackness of the panel oxidized under identical conditions but without the ultrasonic energy. The oxidizing solution of the present example was an aqueous solution of sulfuric acid and potassium permanganate, with a pH of less than 1 used at a temperature of 20 degrees Celsius.
The following example is an illustration whereby boron nitride particles were codeposited in a hard metallic matrix. It should be noted that the present invention is not limited to the type of bath used herein, but in general is for electroless deposits of the various metals and alloys. Moreover, the invention is not limited to the specific particles used, or method of altering the surface of the coating.
In the current example an electroless nickel plating bath, NiSlip 25 sold by Surface Technology, Inc., was used to provide a Ni—P type alloy with boron nitride particles. These particles had a mean particle size of about one micron. The bath was operated at a pH of 6.3 and a temperature of about 170 degrees F.
Four steel panels, manufactured by Taber Industries for use in their Taber wear test equipment, after normal cleaning and activation were plated for 65 minutes under the above conditions. A cross sectional inspection of the coating on a witness panel plated simultaneously with the four Taber panels revealed a quantity of about 10 to 15% codeposited boron nitride particles. Two of these coated panels were then treated by immersion in an oxidizing solution which caused a distinct change in the appearance of the coating surface to a black color from the matte metallic color of the untreated coated panels. The oxidizing solution of the present example was an aqueous solution of sulfuric acid and potassium permanganate, with a pH of less than 1 used at a temperature of 20 degrees Celsius for an immersion time of 40 seconds. All four panels were then heat treated to 400 degrees Celsius for one hour.
Taber wear testing on all four panels of the present example was then implemented in accordance with the instructions provided by Taber Industries, with freshly refaced CS10 wheels with a 1,000 gram load, at ambient temperature for 100 cycles. The results of this Taber wear testing were an average of 0.0015 grams of weight loss for the two panels in the as-plated coating condition, and 0.0005 grams of weight loss for the two panels that were coated and blackened as above. As the Taber test implemented in this example is a measure of weight loss as an indication of wear under this mechanism, the testing in this example demonstrated the unforeseen effect of the blackening treatment to increase the wear resistance of this variation of a composite coating of a low phosphorous alloy of nickel and phosphorous and approximately 10 to 15% boron nitride particles by volume.
The following example is an illustration whereby diamond particles were codeposited in a hard metallic matrix. It should be noted that the present invention is not limited to the type of bath used herein, but in general is for electroless deposits of the various metals and alloys. Moreover, the invention is not limited to the specific particles used, or method of altering the surface of the coating.
In the current example an electroless nickel plating bath, NiPlate 830 sold by Surface Technology, Inc., was used to provide a Ni—P type alloy with diamond particles, also known as CDC-2. The bath was operated at a pH of 6.3 and a temperature of 168 degrees F.
Four steel panels, manufactured by Taber Industries for use in their Taber wear test equipment, after normal cleaning and activation were plated for 120 minutes under the above conditions. A cross sectional inspection of the coating on a witness panel plated simultaneously with the four Taber panels revealed a quantity of about 25 to 30% codeposited diamond particles. Two of these coated panels were then treated by immersion in an oxidizing solution which caused a distinct change in the appearance of the coating surface to a black color from the light gray color of the untreated coated panels. The oxidizing solution of the present example was an aqueous solution of sulfuric acid and potassium permanganate, with a pH of less than 1 used at a temperature of 20 degrees Celsius for an immersion time of 105 seconds. All four panels were then heat treated to 400 degrees Celsius for one hour,
Taber wear testing on all four panels of the present example was then implemented in accordance with the instructions provided by Taber Industries, with freshly refaced CS10 wheels with a 1,000 gram load, at ambient temperature for 1,000 cycles. The results of this Taber wear testing were an average of 0.011 grams of weight loss for the two panels in the as-plated coating condition, and 0.0045 grams of weight loss for the two panels that were coated and blackened as above. As the Taber test implemented in this example is a measure of weight loss as an indication of wear under this mechanism, the testing in this example demonstrated the unforeseen effect of the blackening treatment to increase the wear resistance of this variation of a composite coating of a low phosphorous alloy of nickel and phosphorous and approximately 25 to 30% diamond particles by volume.
The following example is an illustration whereby PTFE particles were codeposited in a hard metallic matrix. It should be noted that the present invention is not limited to the type of bath used herein, but in general is for electroless deposits of the various metals and alloys. Moreover, the invention is not limited to the specific particles used, or method of altering the surface of the coating.
In the current example an electroless nickel plating bath, NiSlip 515 sold by Surface Technology, Inc., was used to provide a Ni—P type alloy with PTFE particles that is essentially free of PFOA and PFOS. The Ni—P alloy of this plating confirms to RoHS, ELV, WEEE and similar regulations. The bath was operated at a pH of 6.1 and a temperature of about 192 degrees F.
Four steel panels, manufactured by Taber Industries for use in their Taber wear test equipment, after normal cleaning and activation were plated for 30 minutes under the above conditions. A cross sectional inspection of the coating on a witness panel plated simultaneously with the four Taber panels revealed a quantity of about 20 to 25% codeposited PTFE particles. Two of these coated panels were then treated by immersion in an oxidizing solution which caused a distinct change in the appearance of the coating surface to a black color from the matte nickel color of the untreated coated panels. The oxidizing solution of the present example was an aqueous solution of ferric chloride, with a pH of less than 1 used at a temperature of 25 degrees Celsius for an immersion time of 90 seconds.
Taber wear testing on all four panels of the present example was then implemented in accordance with the instructions provided by Taber Industries, with freshly refaced CS10 wheels with a 1,000 gram load, at ambient temperature for 100 cycles. The results of this Taber wear testing were an average of 0.009 grams of weight loss for the two panels in the as-plated coating condition, and 0.011 grams of weight loss for the two panels that were coated and blackened as above. As the Taber test implemented in this example is a measure of weight loss as an indication of wear under this mechanism, the testing in this example demonstrated the unforeseen effect of the blackening treatment to have essentially no effect on the wear resistance of this variation of a composite coating of a medium phosphorous alloy of nickel and phosphorous and approximately 20 to 25% PTFE particles by volume.
This patent application claims priority to U.S. Provisional Patent Application No. 61/852,939, filed on Mar. 22, 2013 and incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61852939 | Mar 2013 | US |
