Patent Application
20190071780
The invention pertains to the field of chains. More particularly, the invention pertains to a chain having an electroless nickel coating containing hard particles for improved resistance to corrosion and wear.
Electroless nickel (EN) plating is an auto-catalytic chemical technique used to deposit a layer of nickel-phosphorus or nickel-boron alloy on a solid workpiece which may be made of metal or plastic. The process relies on the presence of a reducing agent, for example hydrated sodium hypophosphite (NaPO2H2.H2O) which reacts with the metal ions to deposit metal on the workpiece. Unlike electroplating, it is not necessary to pass an electric current through the solution to form a deposit on the workpiece. This plating technique is used to prevent corrosion and wear. EN techniques can also be used to manufacture composite coatings by suspending powder in a bath.
Another coating that may be applied to an article or workpiece is a plasma vapor deposition (PVD). PVD is a vacuum deposition method which may be used to produce thin films on an article. PVD uses a physical process, such as heating or sputtering, to produce a vapor of material which is then deposited on the article or object.
A method of improving the wear and corrosion characteristics of a chain by applying a wear resistant electroless nickel coating containing hard particles to chain links and pins of a chain. The coating reduces the friction on the chain links and associated chain components, such as pins, bushings, rockers and other components. The hard particles contained in the coating may be a carbide or nitride formed using the following elements: silicon, boron, chromium or vanadium. The coating may contain a combination of carbide or nitrides. The hard particles may additional include natural diamond and/or synthetic diamond-like carbon (DLC) particles.
Chain links and chain pins when assembled together form a chain. Chains undergo wear due to friction between the chain links and other engine components, friction between associated chain links of the same chain and friction between the links and associated chain components, which can include bushings, rollers, pins and rocker pins. An example of a chain 38 with rollers is shown in
One example of a chain link and its associated components is shown in
In the present invention, a chain link 10, 30, 31, 40, 41 and/or associated components such as chain pins 14, 33, 43, roller 32, and bushings 15, 35, 45 receive an electroless nickel coating which has embedded hard particles. The electroless nickel coating with hard particles creates a wear resistant and low friction coating which decreases wear and friction in the portions of the chain that contact each other or contact other chain or engine components, improving the performance of the chain. Furthermore, by applying the electroless nickel coating with hard particles to the link surfaces that come into contact with engine components, such as arms, guides and sprockets, the wear performance (e.g. resisting wear) is improved.
Referring to
A first step in the method of applying an electroless nickel coating including hard particles to a base material of the chain link and/or chain components is to rinse the base metal of the chain links and/or components with water. Tap water at room temperature is preferably used at this step (step 100), although it will be understood that the water could be filtered and recycled, or heated or cooled, and solvents or surfactants might be added, as might be desired for a particular application. The rinsing of the chain links and/or chain components may take place for at least two minutes. The rinse time may be longer than two minutes and may be influenced by the rinse quality, temperatures and agitation.
Then, the chain links and/or chain components are cleaned using an alkaline agent (step 102) to prevent and cleanse any dirt and remove any foreign contaminants including rust. The alkaline cleaning agent may contain a combination of hydroxide, carbonate, silicates, phosphates and other organic surfactants and is applied at a temperature of 160-180° F. for 5 minutes. The alkaline agent is then rinsed from the chain links and/or chain components, again preferably using tap water at room temperature (step 104). The alkaline agent is rinsed from the chain links and/or chain components for two minutes or greater.
After the chain links and/or chain components are rinsed, they undergo electro-cleaning. In this process, the chain links and/or chain components are connected to a positive (anode) side of a rectifier.
The electro-cleaning tales place between 165° F.-185° F. for 5 minutes at 30 amps per square foot (ASF) (step 106). Alkaline cleaning blends use an electrolyte which contains a mixture of alkaline material to provide high conductivity and alkalinity. Due to the lower cost, sodium salts are frequently used. However, potassium based electro-cleaners have better solubility, lower electrical resistance, and better throwing power.
Prior to immersing the chain links and/or chain components into the acid bath of step 112, it is important to remove any contaminants that cause destabilization of the acid bath. Therefore, the chain links and/or chain components preferably rinsed at least twice after the cleaning, again preferably with tap water at room temperature (steps 108, 110). The advantage to rinsing the chain links and/or chain components twice is to get rid of any solution that may have stayed with the chain links and/or chain components which might be carried to the next step.
Next, the chain links and/or chain components are immersed in an acid bath (step 112). The acid bath may contain sulfuric and/or hydrochloric acid, which is activated by diluting the acid at room temperature with distilled water until an appropriate concentration range is reached. The concentration range is preferably 5-10% for sulfuric acid and 30-50% for hydrochloric acid.
The chain links and/or chain components are then rinsed at least twice, again preferably with tap water at room temperature, for at least one minute each (steps 114, 116).
The chain links and/or chain components are then deposited in a bath to receive the electroless nickel coating including hard particles (step 118). In one embodiment, the bath includes de-ionized water and silicon carbide (SiC) of 0.5 Kg/L at a temperature of 180° F.-190° F. at a pH of 4.8-5.2. In another embodiment, the bath includes de-ionized water and silicon carbide (SiC) of 0.5 Kg/L at a temperature of 185° F. at a pH of 5.0. The coating time varies and depends on the coating thickness preferred. The coating rate is approximately 6 microns per hour. A thickness between 14 to 25 microns is ideal to reduce chain wear, with 25 microns being preferred.
The bath solution is agitated when the coating is being applied to the chain links and/or chain components to maintain bath homogeneity and consistent finish, for example by air blowers or mechanical agitation. A filter of at least 10 microns or finer may be used with the bath and may be part of a filter bag system.
In other embodiments, other carbides or nitrides formed using the following elements: boron, chromium or vanadium may be used to form boron nitrate, boron carbide, chromium carbide, chromium nitride, and vanadium carbide, and vanadium nitride. The temperature and the pH as discussed above would be used for these other carbide and nitrides. Additionally, the hard particles may also be comprised of natural diamond and synthetic diamond-like carbon (DLC) particles.
It should be noted that the concentration of hard particles in the plating bath and plating rate would change based on particle type. For example, for boron nitride particles, the concentration of boron nitride particles needs to be 100 g/L of solution and plating rate is about 19 microns per hour.
The chain links and/or chain components are then rinsed at least twice, again preferably with tap water at room temperature (steps 120, 122) for at least two minutes.
The chain links and/or chain components are then dried (step 124), for example by compressed air, and the method ends.
Evaluations were performed to determine the wear characterization of electroless nickel coated links containing hard particles of silicon carbide. The wear test results have shown improvement in wear performance.
The chains were run at 5000 rpm for 100 hours using oil with 0.2% soot and 1000N of torque. The performance was measured by percent of chain elongation and test hours.
In order to measure chain wear, the center distance (CD) elongation of chain at a given speed and tension over time is measured. Center distance is the distance between the shaft centers of a chain and two-sprocket system. Chain center distance is measured at time intervals during the test. The amount of chain elongation from a new chain can be calculated at each time interval using the following equation:
Where:
t0=time when the chain center distance is measured at the start of the test and is considered to be a “new” chain
t1=time when the chain center distance is measured after wear at each time interval
As shown in
The chains were run at 5000 rpm for 100 hours using a high acid number oil (acidic oil) with 0.2% soot and 1000N of torque.
In order to measure chain wear, the center distance (CD) elongation of chain at a given speed and tension over time is measured. Center distance is the distance between the shaft centers of a chain and two-sprocket system. Chain center distance is measured at each time interval. The amount of chain elongation that is representative of chain wear is calculated using the equation below.
As shown in
Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2016/021701 | 3/10/2016 | WO | 00 |
