US20120297825A1

US20120297825A1 - White Tungsten Carbide Jewelry Article

Info

Publication number: US20120297825A1
Application number: US13/113,690
Authority: US
Inventors: Glenn A. Miller
Original assignee: Stuller Inc
Current assignee: Stuller Inc
Priority date: 2011-05-23
Filing date: 2011-05-23
Publication date: 2012-11-29
Also published as: CA2776634A1

Abstract

An improved jewelry article with a brilliant, preferably white, coating securely bonded to a substrate. The coating comprises predominantly chromium and, where a white finish is desired, a platinum group metal, preferably platinum. The substrate comprises predominantly tungsten carbide and a substantial amount of metal, preferably nickel. The coating is applied to the substrate using vapor deposition, such as physical vapor deposition. The metal and especially nickel will facilitate adhesion between the chromium in the coating and the substrate. The vapor deposition will further provide for superior adhesion as compared to traditional plating techniques. The improved jewelry article will maintain the brilliant, preferably white, finish of the coating due to the hard scratch resistant predominantly chromium coating and the improved adhesion between the coating and substrate.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates generally to the field of coated jewelry in general and more specifically to tungsten carbide jewelry coated with a wear-resistant layer.
2. Prior Art
The use of tungsten carbide for jewelry is well known in the art. Tungsten carbide can be used to create any article of jewelry but is particularly popular in crafting wedding bands and particularly men's wedding bands. Tungsten carbide is known for its hardness and density, making it a suitable material for use in jewelry that will be worn everyday or subjected to harsh conditions. Tungsten carbide rings are known for their dark, lustrous gray color. There is a market for jewelry, particularly rings, in the distinct color of tungsten carbide, and the jewelry can be polished to a minor-like shine which is easily retained because of the hardness of the material.
There are many other traditional metals for use in jewelry and particularly wedding bands. The most common metal for use in wedding bands is gold. Whether yellow, white or rose in color, gold is popular for jewelry, particularly wedding bands because it is traditional and easily engraved. However, gold is not as durable as tungsten carbide and may need to be repolished due to scratching. Platinum is another popular metal for jewelry, particularly wedding bands. However, platinum is one of the most valuable of the precious metals, making it cost prohibitive to some potential buyers. Silver is a cost effective alternative to platinum and provides the same white color and can be polished to a similar brilliant shine. However, unlike either white gold or platinum, common silver alloys easily tarnish and must be polished regularly to maintain their finish.
White gold, platinum, and silver have one important thing in common, their brilliant white color. This color gives jewelry made of these metals a classic, understated appearance and makes all three of these precious metals very popular choices for jewelry, especially wedding rings. As discussed above, rings made of tungsten carbide have a distinctive dark gray color similar to that of hematite and not the brilliant white color of white gold, platinum, and silver. However, jewelry, particularly rings, made of tungsten carbide overcomes some of the problems associated with other precious metals. For instance, unlike gold, tungsten carbide is scratch resistant; unlike platinum, tungsten carbide is cost efficient. Lastly, unlike silver, tungsten carbide does not require constant maintenance. Therefore, in light of the above, there is a distinct need for a jewelry article comprising tungsten carbide that meets the following objectives.

OBJECTS OF THE INVENTION

It is an object of the invention to provide an improved jewelry article that comprises tungsten carbide and is white in color.
It is yet another object of the invention to provide an improved jewelry article that comprises tungsten carbide and is white in color due to a coating affixed to the tungsten carbide.
It is still another object of the invention to provide an improved jewelry article that combines the durability of tungsten carbide with the aesthetic appeal of platinum group metals.
It is a further object of the invention to provide an improved jewelry article that is resistant to scratching.
It is a still further object of the invention to provide a coating that will vigorously adhere to a tungsten carbide jewelry article.

SUMMARY OF THE INVENTION

The invention comprises an improved jewelry article with a brilliant, preferably white coating bonded to a substrate comprising tungsten carbide. The improved jewelry article will maintain the brilliant, white finish of the coating due to increased scratch resistance and improved adhesion between the coating and substrate. The coating comprises chromium and a platinum group metal, preferably platinum. The substrate comprises tungsten carbide and an effective amount of metal, and especially nickel. The coating is bonded to the substrate using vapor deposition. The result is a coating that provides a brilliant, white finish that is resistant to scratching and that strongly adheres to the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of various jewelry articles that can be made according to the present invention.

FIG. 2 is a perspective view of a ring made according to the present invention.

FIG. 2A is a cross-section of the ring shown in FIG. 2 with the coating shown enlarged for illustration purposes.

DETAILED DISCLOSURE OF THE INVENTION

An improved jewelry article 1 is disclosed. Improved jewelry article 1 can be a variety of jewelry pieces such as rings 2, earrings 3, pendants 4, cufflinks 5, chains 6, bracelets 7, necklaces 8, money clips 9 or any other accessory for which the user desires a brilliant long lasting finish. The improvements disclosed herein are particularly useful on jewelry articles 1 which endure particularly rough or sustained wear such as wedding bands or money clips 9 carried in the user's pocket.
The improved jewelry article 1 provides the desired brilliant white finish similar to that commonly found in white gold, platinum, and silver articles or custom nickel plated articles. The durability of the article is simultaneously improved by applying a coating 11 that will sustain the polished finish through increased wear and tear. Furthermore, the overall cost of the jewelry article 1 may be controlled by applying coating 11, comprising a small percentage of a platinum group metal over a substrate 10 which comprises more cost efficient materials including tungsten carbide.
Substrate 10 of improved jewelry article 1 comprises tungsten carbide. Tungsten carbide is known for its durability, resistance to scratching and brilliant dark finish. Jewelry articles, particularly men's wedding bands, comprising tungsten carbide commonly include nickel as binder, and nickel is a common binder for tungsten carbide articles in general. It increases the corrosion resistance of the tungsten carbide. In the present embodiment, the nickel binder percentage has been increased to exploit another property of nickel which is not typically important in tungsten carbide articles, nickel's ability to alloy with metals, and particularly chromium
In a preferred embodiment, the formulation of the starting materials of the substrate by weight is about 22 Kg tungsten carbide, 13.5 Kg titanium carbide, 10.5 Kg nickel, 3.5 Kg molybdenum, 0.5 Kg chromium, and 5 Kg rubber binder. All of the foregoing are combined as powders or shot and thoroughly mixed together. As mentioned below, the rubber binder will vaporize during manufacturing. Thus, the nickel will form about 21 percent by weight of the finished jewelry article, the molybdenum will form about 7 percent by weight of the finished article, and the chromium will form about 1 percent by weight of the finished article. Accordingly, total metal in the finished article will be about 29 percent by weight, in the preferred embodiment.
In one embodiment of manufacturing substrate 10 in which improved jewelry article 1 is a ring, a rubber binder is combined with the other components of substrate and poured into a metal mold and pressed via hydraulic press for approximately 10 seconds. The pressure applied can be between 160 Kg/cm²to 210 Kg/cm². The amount of pressure applied varies directly with the size of the ring being manufactured, such that the pressure applied to manufacture a size 6 ring will be less than the pressure applied to manufacture a size 13 ring.
The molded substrate is then heated from ambient temperature to approximately 550 degrees Celsius. The temperature is held at 550 degrees Celsius for approximately 2 hours to allow rubber binder to vaporize. The temperature is then steadily increased to a target temperature of approximately 1400 degrees Celsius which is reached at approximately 17 hours into the manufacturing process. The temperature peak of 1400 degrees Celsius is below the melting point of elemental nickel which is 1455 degrees Celsius. However, combining nickel with the other components of the substrate is believed to lower its melting point such that the nickel in the substrate will melt at or below the temperature peak of the manufacturing process, 1400 degrees Celsius. The manufacturing process for the substrate is more thoroughly discussed in pending U.S. patent application Ser. No. 12/904,349, which is hereby incorporated by reference in its entirety.
Another advantageous property of nickel is that it readily wets tungsten carbide, such that the tungsten carbide within the substrate should become surrounded by nickel upon its melting. Due to the melting of nickel and the wetting of tungsten carbide, the nickel should be well distributed throughout the completed substrate. This should make the nickel readily available for binding with the coating 11. Similarly, molybdenum will be present throughout the substrate via mixing prior to sintering.
In the development of the present invention, the desired brilliant white finish was originally sought via the use of several brilliant white metals. In one attempt, a substantially pure rhodium coating was applied to the substrate. While a brilliant white finish was achieved, the jewelry article formed therein did not have the desired durability, and the coating spalled off easily. In yet another attempt, a pure chromium coating was applied to enhance durability. Chromium was selected because of its hardness, 8.5 on the Mohs scale. However, while durability and scratch resistance were achieved, the color of the coating was not the desired brilliant white finish reminiscent of white gold, platinum, and silver Finally, the present embodiment combining chromium with a platinum group metal was selected. It achieves the desired results of hardness, scratch resistance and brilliant white finish.
In a preferred embodiment of the present invention, coating 11 is comprised predominantly of chromium and includes a platinum group metal. The preferred coating 11 is approximately 97-99% chromium, about 0.5-3% platinum, and about 0.01-0.03% each of nickel, copper, and carbon. It is believed that any of the platinum group metals can be used in place of the platinum in the coating to achieve substantially similar results. Thus, it is believed that ruthenium, rhodium, osmium, iridium, or palladium could be substituted for platinum in coating 11.
It should be noted that the platinum group metals are utilized primarily for color. They are particularly suitable where a white coating is desired. Other metals may be utilized where a different coating of a different color is desired.
In the manufacturing process, the chromium vapor solution is mixed with a platinum group metal and deposited on the substrate utilizing vapor deposition. There are two forms of vapor deposition: physical vapor deposition and chemical vapor deposition. The major physical vapor deposition methods are ion plating, ion implantation, sputtering and laser surface alloying. In a preferred embodiment, physical vapor deposition in the form of sputtering deposition is used to apply coating to substrate to form improved jewelry article 1. However, the other forms of physical vapor deposition and chemical vapor deposition are believed to be suitable for applying coating 11 to the substrate to form improved jewelry article.
The basic premise of physical vapor deposition is depositing a coating over an entire object or surface using dry vacuum deposition methods. There are three basic elements to all reactive physical vapor deposition processes: a method for deposition of the metal, an active gas, and plasma bombardment of the coating to ensure the metal deposits in dense, hard fashion. The preferred process of physical vapor deposition, sputtering, is an etching process which alters the physical properties of the surface of the substrate. Sputtering can be used to deposit metals, alloys, compounds, and dielectrics.
Sputtering involves a gas plasma discharge between a cathode plating material and an anode substrate. The reactive gas ions, which are positively charged, are attracted to and accelerated into the cathode. The force of the impact knocks atoms off of the cathode. Those atoms impact the anode and plate the substrate with the coating.
Chemical vapor deposition is a subset of physical vapor deposition, and the distinction between physical vapor deposition and chemical vapor deposition continues to blur as new technologies develop. Sputtering can also be done with chemical vapor deposition, and the basic elements of chemical vapor deposition are formation of a reactive gas mixture, mass transport of the reactant gas through a boundary layer to the substrate, adsorption of the reactants on the substrate, and reaction of the adsorbents to faun the deposit.
As stated above, the preferred embodiment of the present invention is an improved jewelry article 1 in which a coating 11 of predominantly chromium is deposited on a substrate 10 of predominantly tungsten carbide utilizing vapor deposition such that a strong adhesion between the substrate 10 and coating 11 yields a brilliant and preferably white finish that is scratch resistant.
The disclosed method is believed to accomplish this result in several ways. There is a high amount of metal and particularly nickel in substrate 10 relative to other tungsten carbide jewelry. Because the nickel is believed to thoroughly melt and spread throughout substrate 10 during the manufacturing process, it is available to alloy with coating 11. Thus, when the chromium and platinum group coating is deposited onto substrate 10, there is a substantial amount of metal and particularly nickel available with which the coating components may interact. Chromium will readily alloy with nickel and molybdenum. Thus, the presence of nickel and molydenum will provide a superior bonding surface for coating 11 than would be provided by tungsten carbide. Accordingly, the presence of the metals, and especially the nickel and molybdenum, in the substrate will allow coating 11 to adhere more strongly to substrate 10. Second, vapor deposition will provide a superior bond between coating 11 and substrate 10 as compared to traditional coating methods such as electroplating. Finally, chromium is quite hard and, once securely fastened to the tungsten carbide substrate, will resist scratching by most substances that would be regularly encountered by a ring on the wearer's hands, even where the wearer may be involved in heavy manual labor.

Example 1

To test the scratch resistance and adhesion of improved jewelry article 1, a test was performed comparing improved jewelry article 1 and a leading competitive product available in the marketplace. The coating of the competitive white coated tungsten carbide product was tested and is believed to have a composition that is 54% gold, 25% rhodium, 16% chromium, and 5% iron. The substrate of the competitive product is further believed to comprise about 85% tungsten carbide by weight. Both improved jewelry article 1 and the competing product were rings. A Grobet 0 file, approximately ¼ inch wide by 3 inches long, was run along the lap side of each ring one time. Scratches were observable with the naked eye in the coating of the competitive ring. No scratches were observable in the coating of the improved ring. After observation with the unaided eye, the rings were studied under a 20× binocular microscope. Upon observation with the microscope, no scratching was observed on the surface of the improved ring. However, scratching on the surface of the competitive ring was

Claims

1. A improved jewelry article comprising:

a substrate having an exterior surface, said substrate comprising predominantly tungsten carbide by weight, said substrate further comprising metal, said metal comprising at least about twenty percent of said substrate by weight;

a coating secured to said substrate via vapor deposition; said coating comprising predominantly chromium.

2. An improved jewelry article according to claim 1 wherein said coating covers substantially all of said exterior surface of said substrate.

3. An improved jewelry article according to claim 2 wherein said metal comprises at least about twenty-seven percent of said substrate by weight.

4. An improved jewelry article according to claim 2 wherein said metal comprises nickel and alloys thereof.

5. An improved jewelry article according to claim 4 wherein said nickel is dispersed throughout said substrate.

6. An improved jewelry article according to claim 5 wherein said metal further comprises molybdenum.

7. An improved jewelry article according to claim 6 wherein said molybdenum is dispersed throughout said substrate.

8. An improved jewelry article according to claim 7 wherein said coating further comprises a metal selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, and platinum.

9. An improved jewelry article according to claim 5 wherein said coating further comprises a metal selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, and platinum.

10. An improved jewelry article according to claim 9 wherein said coating is white.

11. An improved jewelry article according to claim 1 wherein said substrate is selected from the group consisting of rings, earrings, necklaces, bracelets, and pendants.

12. An improved jewelry article according to claim 11 wherein said substrate is a ring.

13. An improved jewelry article according to claim 1 wherein said substrate is formed by sintering.

14. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article comprising:

applying a coating to a substrate via vapor deposition, said coating comprising predominantly chromium;

said substrate having an exterior surface, said substrate further comprising predominantly tungsten carbide by weight, said substrate further comprising metal, said metal comprising at least about twenty percent of said substrate by weight.

15. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 14 wherein said coating is applied to substantially all of said exterior surface of said substrate.

16. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 15 wherein said metal comprises at least about twenty-seven percent of said substrate by weight.

17. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 15 wherein said metal comprises nickel.

18. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 17 wherein said nickel is dispersed throughout said substrate.

19. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 18 wherein said metal further comprises molybdenum.

20. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 19 wherein said molybdenum is dispersed throughout said substrate.

21. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 20 wherein said coating further comprises a metal selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, and platinum.

22. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 18 wherein said coating further comprises a metal selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, and platinum.

23. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 22 wherein said coating is white.

24. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 14 wherein said substrate is selected from the group consisting of rings, earrings, necklaces, bracelets, and pendants.

25. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 24 wherein said substrate is a ring.

26. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 15 wherein said vapor deposition comprises physical vapor deposition.

27. A method of applying a scratch resistant coating with a high degree of adhesion to a jewelry article according to claim 26 wherein said physical vapor deposition comprises sputtering.

28. An improved jewelry article according to claim 27 wherein said substrate is formed by sintering.