Low pressure coated article

FIELD OF THE INVENTION

[0001] This invention relates to articles, particularly brass articles, having a multi-layered decorative and protective coating having the appearance or color of nickel which is deposited by low pressure vapor deposition.

BACKGROUND OF THE INVENTION

[0002] It is currently the practice with various brass articles such as faucets, faucet escutcheons, door knobs, door handles, door escutcheons and the like to first buff and polish the surface of the article to a high gloss and to then apply a protective organic coating, such as one comprised of acrylics, urethanes, epoxies and the like, onto this polished surface This system has the drawback that the buffing and polishing operation, particularly if the article is of a complex shape, is labor intensive. Also, the known organic coatings are not always as durable as desired, and are susceptible to attack by acids. It would, therefore, be quite advantageous if brass articles, or indeed other articles, either plastic, ceramic, or metallic, could be provided with a coating which provided the article with a decorative appearance as well as providing wear resistance, abrasion resistance and corrosion resistance. It is known in the art that a multi-layered coating can be applied to an article which provides a decorative appearance as well as providing wear resistance, abrasion resistance and corrosion resistance. This multi-layer coating includes a decorative and protective color layer of a refractory metal nitride such as a zirconium nitride or a titanium nitride. This color layer, when it is zirconium nitride, provides a brass color, and when it is titanium nitride provides a gold color.

[0003] U.S. Pat. Nos. 5,922,478; 6,033,790 and 5,654,108, inter alia, describe a coating which provides an article with a decorative color, such as polished brass, provides wear resistance, abrasion resistance and corrosion resistance It would be very advantageous if a coating could be provided which provided substantially the same properties as the coatings containing zirconium nitride or titanium nitride but instead of being brass colored or gold colored was nickel colored. The present invention provides such a coating

SUMMARY OF THE INVENTION

[0004] The present invention is directed to an article such as a plastic, ceramic or metallic article having a decorative and protective multi-layer coating deposited on at least a portion of its surface. More particularly, it is directed to an article or substrate, particularly a metallic article such as stainless steel, aluminum, brass or zinc, having deposited on its surface multiple superposed layers of certain specific types of materials. The coating is decorative and also provides corrosion resistance, wear resistance and abrasion resistance. The coating provides the appearance of nickel, i.e. has a nickel color tone. Thus, an article surface having the coating thereon simulates a nickel surface.

[0005] The article first has deposited on its surface one or more electroplated layers. On top of the electroplated layers is then deposited, by vapor deposition such as physical vapor deposition, a vapor deposited stack layer. A first layer deposited directly on the surface of the substrate is comprised of nickel. The first layer may be monolithic or it may consist of two different nickel layers such as, for example, a semi-bright nickel layer deposited directly on the surface of the substrate and a bright nickel layer superimposed over the semi-bright nickel layer. Disposed over the electroplated layers is a strike layer comprised of a refractory metal or refractory metal alloy such as zirconium, titanium, hafnium, tantalum or zirconium-titanium alloy, preferably zirconium, titanium or zirconium-titanium alloy. Over the layer comprised of refractory metal or refractory metal alloy is a layer comprised of a stack or sandwich layer containing alternating layers of refractory metal compound or refractory metal alloy compound and a refractory metal or refractory metal alloy. Over the stack layer is a color layer comprised of a refractory metal nitride or refractory metal alloy nitride wherein the refractory metal nitride or refractory metal alloy nitride is lightly nitrided, that is to say contains a small amount, i.e. less than stoichiometric amount, of nitrogen. Generally this amount of nitrogen is between about 6 to about 45 atomic percent. The protective color layer is deposited at relatively low pressures in the vacuum coating chamber. These relatively low pressures are generally below about 8 millitorr, preferably below about 5 millitorr, and more preferably below about 3 millitorr. This low pressure deposition results in improved corrosion resistance and improved mechanical properties, particularly improved scratch resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]
FIG. 1 is a cross sectional view of a portion of the substrate having a multi-layer coating comprising a duplex nickel base coat and a stacked color and protective layer directly on the top nickel layer;

[0007]
FIG. 2 is a view similar to FIG. 1 except that the refractory metal, such as zirconium, strike layer is present intermediate the top nickel layer and the stacked or sandwich layer;

[0008]
FIG. 3 is a view similar to FIG. 2 except that a chromium layer is present intermediate the top nickel layer and the refractory metal strike layer;

[0009]
FIG. 4 is a view similar to FIG. 3 except that a refractory metal oxide layer is present on the stacked layer; and

[0010]
FIG. 5 is a cross sectional view similar to FIG. 1 except that the stacked layer is directly on the article surface without any intervening electroplated layers.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0011] The article or substrate 12 can be comprised of any material onto which a plated layer can be applied, such as plastic, e.g., ABS, polyolefin, polyvinylchloride, and phenolformaldehyde, ceramic, metal or metal alloy. In one embodiment it is comprised of a metal or metallic alloy such as copper, steel, brass zinc, aluminum, nickel alloys and the like.

[0012] In the instant invention, as illustrated in FIGS. 1-4, a first layer or series of layers is applied onto the surface of the article by plating such as electroplating. A second series of layers is applied onto the surface of the electroplated layer or layers by vapor deposition. The electroplated layers serve, inter alia, as a base coat which levels the surface of the article. In one embodiment of the instant invention a nickel layer 13 may be deposited on the surface of the article. The nickel layer may be any of the conventional electroplated nickels e.g., bright nickel, semi-bright nickel, satin nickel, etc. The nickel layer 13 may be deposited on at least a portion of the surface of the substrate 12 by conventional and well-known electroplating processes. These processes include using a conventional electroplating bath such as, for example, a Watts bath as the plating solution. Typically such baths contain nickel sulfate, nickel chloride, and boric acid dissolved in water. All chloride, sulfamate and fluoroborate plating solutions can also be used. These baths can optionally include a number of well known and conventionally used compounds such as leveling agents, brighteners, and the like. To produce specularly bright nickel layer at least one brightener from class I and at least one brightener from class II is added to the plating solution. Class I brighteners are organic compounds which contain sulfur. Class II brighteners are organic compounds which do not contain sulfur. Class II brighteners can also cause leveling and, when added to the plating bath without the sulfur-containing class I brighteners, result in semi-bright nickel deposits. These class I brighteners include alkyl naphthalene and benzene sulfonic acids, the benzene and naphthalene di- and trisulfonic acids, benzene and naphthalene sulfonamides, and sulfonamides such as saccharin, vinyl and allyl sulfonamides and sulfonic acids. The class II brighteners generally are unsaturated organic materials such as, for example, acetylenic or ethylenic alcohols, ethoxylated and propoxylated acetylenic alcohols, coumarins, and aldehydes. These class I and class II brighteners are well known to those skilled in the art and are readily commercially available. They are described, inter alia, in U.S. Pat. No. 4,421,611 incorporated herein by reference.

[0013] The nickel layer can be comprised of a monolithic layer such as semi-bright nickel, satin nickel or bright nickel, or it can be a duplex layer containing two different nickel layers, for example, a layer comprised of semi-bright nickel and a layer comprised of bright nickel. The thickness of the nickel layer is generally a thickness effective to level the surface of the article and to provide improved corrosion resistance. This thickness is generally in the range of from about 2.5 μm, preferably about 4 μm to about 90 μm.

[0014] As is well known in the art before the nickel layer is deposited on the substrate the substrate is subjected to acid activation by being placed in a conventional and well known acid bath.

[0015] In one embodiment as illustrated in FIGS. 1-4, the nickel layer 13 is actually comprised of two different nickel layers 14 and 16. In one embodiment layer 14 is comprised of semi-bright nickel while layer 16 is comprised of bright nickel. This duplex nickel deposit provides improved corrosion protection to the underlying substrate. The semi-bright, sulfur-free plate 14 is deposited by conventional electroplating processes directly on the surface of substrate 12. The substrate 12 containing the semi-bright nickel layer 14 is then placed in a bright nickel plating bath and the bright nickel layer 16 is deposited on the semi-bright nickel layer 14.

[0016] The thickness of the semi-bright nickel layer and the bright nickel layer is a thickness at least effective to provide improved corrosion protection and/or leveling of the article surface. Generally, the thickness of the semi-bright nickel layer is at least about 1.2 μm, preferably at least about 2.5 μm, and more preferably at least about 3.8 μm. The upper thickness limit is generally not critical and is governed by secondary considerations such as cost. Generally, however, a thickness of about 40 μm, preferably about 25 μm, and more preferably about 20 μm should not be exceeded. The bright nickel layer 16 generally has a thickness of at least about 1 μm, preferably at least about 3 μm, and more preferably at least about 5 μm. The upper thickness range of the bright nickel layer is not critical and is generally controlled by considerations such as cost. Generally, however, a thickness of about 60 μm, preferably about 50 μm, and more preferably about 40 μm should not be exceeded. The bright nickel layer 16 also functions as a leveling layer which tends to cover or fill in imperfections in the substrate.

[0017] In one embodiment, as illustrated in FIGS. 3 and 4, disposed between the nickel layer 13 and the vapor deposited layers are one or more additional electroplated layers 21. These additional electroplated layers include but are not limited to chromium, tin-nickel alloy, and the like. When layer 21 is comprised of chromium it may be deposited on the nickel layer 13 by conventional and well known chromium electroplating techniques. These techniques along with various chrome plating baths are disclosed in Brassard, “Decorative Electroplating—A Process in Transition”, Metal Finishing, pp. 105-108, June 1988; Zaki, “Chromium Plating”, PF Directory, pp. 146-160; and in U.S. Pat. Nos. 4,460,438; 4,234,396; and 4,093,522, al of which are incorporated herein by reference.

[0018] Chrome plating baths are well known and commercially available. A typical chrome plating bath contains chromic acid or salts thereof, and catalyst ion such as sulfate or fluoride. The catalyst ions can be provided by sulfuric acid or its salts and fluosilicic acid. The baths may be operated at a temperature of about 112°-116° F. Typically in chrome plating a current density of about 150 amps per square foot, at about 5 to 9 volts is utilized.

[0019] The chrome layer generally has a thickness of at least about 500 Å, preferably at least about 0.1 μm, and more preferably at least about 0.2 μm. Generally, the upper range of thickness is not critical and is determined by secondary considerations such as cost. However, the thickness of the chrome layer should generally not exceed about 1.5 μm, preferably about 1.2 μm, and more preferably about 1 μm.

[0020] Instead of layer 21 being comprised of chromium it may be comprised of tin-nickel alloy, that is an alloy of nickel and tin. The tin-nickel alloy layer may be deposited on the surface of the substrate by conventional and well known tin-nickel electroplating processes. These processes and plating baths are conventional and well known and are disclosed, inter alia, in U.S. Pat. Nos. 4,033,835; 4,049,508; 3,887,444; 3,772,168 and 3,940,319, all of which are incorporated herein by reference.

[0021] The tin-nickel alloy layer is preferably comprised of about 60-70 weight percent tin and about 30-40 weight percent nickel, more preferably about 65% tin and 35% nickel representing the atomic composition SnNi. The plating bath contains sufficient amounts of nickel and tin to provide a tin-nickel alloy of the afore-described composition.

[0022] A commercially available tin-nickel plating process is the NiColloy™ process available from ATOTECH, and described in their Technical Information Sheet No: NiColloy, Oct. 30, 1994, incorporated herein by reference.

[0023] The thickness of the tin-nickel alloy layer 20 is generally at least about 0.25 μm, preferably at least about 0.5 μm, and more preferably at least about 1 μm. The upper thickness range is not critical and is generally dependent on economic considerations. Generally, a thickness of about 50 μm, preferably about 25 μm, and more preferably about 12 μm should not be exceeded.

[0024] A sandwich or stack layer 32 comprised of alternating layers of refractory metal compound or refractory metal alloy compound 34 and refractory metal or refractory metal alloy 36 is deposited on the top electroplated layer such as the chromium layer 21. The stack layer 32 is deposited by vapor deposition such as physical vapor deposition or chemical vapor deposition. The physical vapor deposition techniques are conventional and well known techniques including cathodic arc evaporation (CAE), reactive cathodic arc evaporation, sputtering, reactive sputtering, and the like. Sputtering techniques and equipment are disclosed, inter alia, in J. Vossen and W. Kern “Thin Film Processes II”, Academic Press, 1991; R. Boxman et al, “Handbook of Vacuum Arc Science and Technology”, Noyes Pub., 1955; and U.S. Pat. Nos. 4,162,954 and 4,591,418, all of which are incorporated herein by reference.

[0025] Briefly, in the sputtering deposition process a refractory metal (such as titanium or zirconium) target, which is the cathode, and the substrate are placed in a vacuum chamber. The air in the chamber is evacuated to produce vacuum conditions in the chamber. An inert gas, such as Argon, is introduced into the chamber. The gas particles are ionized and are accelerated to the target to dislodge titanium or zirconium atoms. The dislodged target material is then typically deposited as a coating film on the substrate.

[0026] In cathodic arc evaporation, an electric arc of typically several hundred amperes is struck on the surface of a metal cathode such as zirconium or titanium The arc vaporizes the cathode material, which then condenses on the substrates forming a coating.

[0027] The refractory metals and refractory metal alloys comprising layers 36 include hafnium, tantalum, titanium, zirconium, zirconium-titanium alloy, zirconium-hafnium alloy, and the like, preferably zirconium, titanium, or zirconium-titanium alloy, and more preferably zirconium or zirconium-titanium alloy.

[0028] The refractory metal compounds and refractory metal alloy compounds comprising layers 34 include hafnium compounds, tantalum compounds, titanium compounds, zirconium compounds, and zirconium-titanium alloy compounds, preferably titanium compounds, zirconium compounds, or zirconium-titanium alloy compounds, and more preferably zirconium compounds. These compounds are selected from oxides, nitrides, carbides and carbonitrides, with the nitrides being preferred. Thus, the titanium compound is selected from titanium nitride, titanium carbide and titanium carbonitride, with titanium nitride being preferred. The zirconium compound is selected from zirconium nitride, zirconium carbide and zirconium carbonitride, with zirconium nitride being preferred.

[0029] In a preferred embodiment the refractory metal compounds and refractory metal alloy compounds comprising layers 34 are the refractory metal nitrides and the refractory metal alloy nitrides. In a more preferred embodiment these refractory metal nitrides and refractory metal alloy nitrides have a low nitrogen content, i.e., substoichiometric of from about 6 to about 45 atomic percent, preferably from about 8 to about 35 atomic percent to have a nickel color.

[0030] The sandwich or stack layer 32 generally has an average thickness of from about 500 Å to about 1 μm, preferably from about 0.1 μm to about 0.85 μm, and more preferably from about 0.15 μm to about 0.75 μm.

[0031] Each of layers 34 and 36 generally has a thickness of at least about 15 Å, preferably at least about 30 Å, and more preferably at least about 50 Å. Generally, layers 34 and 36 should not be thicker than about 0.38 μm, preferably about 0.25 μm, and more preferably about 0.1 μm.

[0032] A method of forming the stack layer 32 is by utilizing sputtering or cathodic arc evaporation to deposit a layer 36 of refractory metal such as zirconium or titanium followed by reactive sputtering or reactive cathodic arc evaporation to deposit a layer 34 of refractory metal nitride such as zirconium nitride or titanium nitride.

[0033] Preferably the flow rate of nitrogen gas is varied (pulsed) during vapor deposition such as reactive sputtering between zero (no nitrogen gas is introduced) to the introduction of nitrogen at a desired value to form multiple alternating layers of metal 36 and metal nitride 34 in the sandwich layer 32.

[0034] The number of alternating layers of refractory metal or refractory metal alloy 36 and refractory metal compound or refractory metal alloy compound layers 34 in sandwich or stack layer 32 is generally at least about 2, preferably at least about 4, and more preferably at least about 6. Generally, the number of alternating layers of refractory metal alloy 36 and refractory metal compound or refractory metal alloy compound in stack layer 32 should generally not exceed about 75, preferably about 50.

[0035] Over the stack layer 32 is a color layer 38. The color layer 38 is comprised of refractory metal nitride or refractory metal alloy nitride wherein said nitride has a low nitrogen content, i.e., substoichiometric, of from about 6 to about 45 atomic percent, preferably from about 8 to about 35 atomic percent to have a nickel color. The color layer is deposited at relatively low pressures in the vapor deposition chamber, such as a physical vapor deposition chamber, this amount of nitrogen provides a nickel colored coating with two types of structures: (1) mainly amorphous metallic refractory metal with textured metal nitride phase with the nano-sized crystal grains preferentially oriented in a certain direction, and (2) highly textured nano-size grains of the metallic refractory metal preferentially oriented in a certain direction. For example, for zirconium the first type of structure is comprised of amorphous metallic zirconium and a small amount of zirconium nitride with a grain size smaller than 50 nm and preferentially oriented on the (111) plane, while the second type of structure is mainly metallic zirconium with a grain size smaller than 80 nm and preferentially oriented in the (112) plane.

[0036] The low processing pressures in the vapor deposition vacuum chamber are generally below about 8 millitorr, preferably below about 5 millitorr, and more preferably below about 3 millitorr. Thus, for example, processing pressures can range from about 1 to about 5 millitorr.

[0037] This low pressure deposition results in improved mechanical properties, particularly abrasion resistance, and improved corrosion resistance.

[0038] Layer 38 has a thickness at least effective to provide a nickel color. Generally, this thickness is at least about 25 Å, and more preferably at least about 500 Å. The upper thickness range is generally not critical and is dependent upon secondary considerations such as cost. Generally a thickness of about 0.75 μm, preferably about 0.6 μm, and more preferably about 0.5 μm should not be exceeded.

[0039] In one embodiment as illustrated in FIGS. 2 and 3 disposed intermediate stack layer 32 and the top electroplated layer is a refractory metal or refractory metal alloy layer 31. The refractory metal layer or refractory metal alloy layer 31 generally functions, inter alia, as a strike layer which improves the adhesion of the stack layer 32 to the top electroplated layer. As illustrated in FIGS. 2 and 3, the refractory metal or refractory metal alloy strike layer 31 is generally disposed intermediate the stack layer 32 and the top electroplated layer. Layer 31 has a thickness which is generally at least effective for layer 31 to function as a strike layer. Generally, this thickness is at least about 60 Å, preferably at least about 120 Å, and more preferably at least about 250 Å. The upper thickness range is not critical and is generally dependent upon considerations such as cost. Generally, however, layer 31 should not be thicker than about 1.2 μm, preferably about 0.4 μm, and more preferably about 0.25 μm.

[0040] In a preferred embodiment of the present invention the refractory metal of layer 31 is comprised of titanium or zirconium, preferably zirconium, and the refractory metal alloy is comprised of zirconium-titanium alloy.

[0041] In one embodiment of the invention as illustrated in FIG. 4 a layer 39 comprised of the reaction products of (i) a refractory metal or metal alloy, (ii) an oxygen containing gas such as oxygen, and (iii) nitrogen is deposited onto stack layer 32. The metals that may be employed in the practice of this invention are those which are capable of forming both a metal oxide and a metal nitride under suitable conditions, for example, using a reactive gas comprised of oxygen and nitrogen The metals may be, for example, tantalum, hafnium, zirconium, zirconium-titanium alloy, and titanium, preferably titanium, zirconium-titanium alloy and zirconium, and more preferably zirconium.

[0042] The reaction products of the metal or metal alloy, oxygen and nitrogen are generally comprised of the metal or metal alloy oxide, metal or metal alloy nitride and metal or metal alloy oxy-nitride.

[0043] Thus, for example, the reaction products of zirconium, oxygen and nitrogen comprise zirconium oxide, zirconium nitride and zirconium oxy-nitride. These metal oxides and metal nitrides including zirconium oxide and zirconium nitride alloys and their preparation and deposition are conventional and well known, and are disclosed, inter alia, in U.S. Pat. No. 5,367,285, the disclosure of which is incorporated herein by reference.

[0044] The layer 39 can be deposited by well known and conventional vapor deposition techniques, including reactive sputtering and cathodic arc evaporation.

[0045] In another embodiment instead of layer 39 being comprised of the reaction products of a refractory metal or refractory metal alloy, oxygen and nitrogen, it is comprised of refractory metal oxide or refractory metal alloy oxide. The refractory metal oxides and refractory metal alloy oxides of which layer 34 is comprised include, but are not limited to, hafnium oxide, tantalum oxide, zirconium oxide, titanium oxide, and zirconium-titanium alloy oxide, preferably titanium oxide, zirconium oxide, and zirconium-titanium alloy oxide, and more preferably zirconium oxide. These oxides and their preparation are conventional and well known.

[0046] Layer 39 is effective in providing improved chemical, such as acid or base, resistance to the coating. Layer 39 containing (i) the reaction products of refractory metal or refractory metal alloy, oxygen and nitrogen, or (ii) refractory metal oxide or refractory metal alloy oxide generally has a thickness at least effective to provide improved chemical resistance. Generally this thickness is at least about 10 Å, preferably at least about 25 Å, and more preferably at least about 40 Å. Layer 39 should be thin enough so that it does not obscure the color of underlying color layer 38. That is to say layer 34 should be thin enough so that it is non-opaque or substantially transparent. Generally layer 39 should not be thicker than about 500 Å, preferably about 150 Å, and more preferably about 100 Å.

[0047] The nickel color of the coating can be controlled or predetermined by controlling the nature of the nickel layer. If the nickel layer 13 is monolithic and the nickel layer is comprised of bright nickel then the color of the coating will generally resemble bright nickel. If the monolithic nickel layer is comprised of semi-bright nickel then the color of the coating will generally resemble semi-bright nickel. If the monolithic nickel layer is comprised of satin nickel then the color of the coating will resemble satin nickel. If the nickel layer 13 is comprised of a duplex nickel layer then the nickel color of the coating will generally depend on the nature of the top nickel layer 16. If the top nickel layer 16 is comprised of bright nickel then the coating will resemble bright nickel. If the top nickel layer is comprised of satin nickel then the coating will resemble satin nickel. If the top nickel layer is comprised of semi-bright nickel then the coating will resemble semi-bright nickel.

[0048] In order that the invention may be more readily understood, the following example is provided. The example is illustrative and does not limit the invention thereto.

EXAMPLE

[0049] Brass faucets are placed in a conventional soak cleaner bath containing the standard and well known soaps, detergents, defloculants and the like which is maintained at a pH of 8.9-9.2 and a temperature of 180-200° F. for about 10 minutes. The brass faucets are then placed in a conventional ultrasonic alkaline cleaner bath. The ultrasonic cleaner bath has a pH of 8.9-9.2, is maintained at a temperature of about 160-180° F., and contains the conventional and well known soaps, detergents, defloculants and the like. After the ultrasonic cleaning the faucets are rinsed and placed in a conventional alkaline electro cleaner bath. The electro cleaner bath is maintained at a temperature of about 140-180° F., a pH of about 10.5-11.5, and contains standard and conventional detergents. The faucets are then rinsed twice and placed in a conventional acid activator bath. The acid activator bath has a pH of about 2.0-3.0, is at an ambient temperature, and contains a sodium fluoride based acid salt. The faucets are then rinsed twice and placed in a bright nickel plating bath for about 12 minutes. The bright nickel bath is generally a conventional bath which is maintained at a temperature of about 130-150° F., a pH of about 4.0, contains NiSO4, NiCL2, boric acid, and brighteners. A bright nickel layer of an average thickness of about 10 μm is deposited on the faucet surface. The bright nickel plated faucets are rinsed three times and then placed in a conventional, commercially available hexavalent chromium plating bath using conventional chromium plating equipment for about seven minutes. The hexavalent chromium bath is a conventional and well known bath which contains about 32 ounces/gallon of chromic acid. The bath also contains the conventional and well known chromium plating additives. The bath is maintained at a temperature of about 112°-116° F., and utilizes a mixed sulfate/fluoride catalyst. The chromic acid to sulfate ratio is about 200:1. A chromium layer of about 0.25 μm is deposited on the surface of the bright nickel layer. The faucets are thoroughly rinsed in deionized water and then dried. The chromium plated faucets are placed in a cathodic arc evaporation plating vessel. The vessel is generally a cylindrical enclosure containing a vacuum chamber which is adapted to be evacuated by means of pumps. A source of argon gas is connected to the chamber by an adjustable valve for varying the rate of flow of argon into the chamber. In addition, a source of nitrogen gas is connected to the chamber by an adjustable valve for varying the rate of flow of nitrogen into the chamber.

[0050] A cylindrical cathode is mounted in the center of the chamber and connected to negative outputs of a variable D.C. power supply. The positive side of the power supply is connected to the chamber wall. The cathode material comprises zirconium.

[0051] The plated faucets are mounted on spindles, 16 of which are mounted on a ring around the outside of the cathode. The entire ring rotates around the cathode while each spindle also rotates around its own axis, resulting in a so-called planetary motion which provides uniform exposure to the cathode for the multiple faucets mounted around each spindle. The ring typically rotates at several rpm, while each spindle makes several revolutions per ring revolution. The spindles are electrically isolated from the chamber and provided with rotatable contacts so that a bias voltage may be applied to the substrates during coating.

[0052] The vacuum chamber is evacuated to a pressure of about 10−5 to 10−7 torr and heated to about 150° C.

[0053] The electroplated faucets are then subjected to a high-bias arc plasma cleaning in which a (negative) bias voltage of about 500 volts is applied to the electroplated faucets while an arc of approximately 500 amperes is struck and sustained on the cathode. The duration of the cleaning is approximately five minutes.

[0054] Argon gas is introduced at a rate sufficient to maintain a pressure of about 1 to 5 millitorr. A layer of zirconium having an average thickness of about 0.1 μm is deposited on the chrome plated faucets during a three minute period. The cathodic arc deposition process comprises applying D.C. power to the cathode to achieve a current flow of about 500 amps, introducing argon gas into the vessel to maintain the pressure in the vessel at about 1 to 5 millitorr and rotating the faucets in a planetary fashion described above.

[0055] After the zirconium layer is deposited a stack layer is applied onto the zirconium layer. A flow of nitrogen is introduced into the vacuum chamber periodically at a flow rate of 10 to 20% of total flow while the arc discharge continues at approximately 500 amperes. The nitrogen flow rate is pulsed, that is to say it changed periodically a flow rate of about 10 to 20% of total flow and a flow rate of about zero. The period of the nitrogen pulsing is one to two minutes (30 seconds to one minute on, then of). The total time for pulsed deposition is about 15 minutes, resulting in a stack of about 10 to 15 layers of a thickness of about 25 Å to about 75 Å for each layer.

[0056] After the stack layer is deposited, the pressure is adjusted to about 1 to 5 millitorr, the nitrogen flow rate is left on at a flow rate of about 10 to 20% of total flow for a period of time of about 5 to 10 minutes to form the color layer on top of the stack layer. After this zirconium nitride layer is deposited, an additional flow of oxygen of approximately 0.1 to 7 standard liters per minute is introduced for a time of thirty seconds to one minute, while maintaining nitrogen and argon flow rates at their previous values. A thin layer of mixed reaction products is formed (zirconium oxy-nitride), with thickness of approximately 50 to 125 Å. The arc is extinguished at the end of this last deposition period, the vacuum chamber is vented and the coated substrates removed.

[0057] While certain embodiments of the invention have been described for purposes of illustration, it is to be understood that there may be various embodiments and modifications within the general scope of the invention.

Low pressure coated article

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