HARDENED COBALT BASED ALLOY JEWELRY AND RELATED METHODS
Hardened cobalt alloys for forming jewelry, including finger rings as well as methods and processes for producing such alloys. In one illustrative embodiment, such an alloy can contain cobalt in an amount of from about 35 wt % to about 65 wt %, in combination with chromium in an amount of from about 16% wt to about 32 wt %, and molybdenum in an amount of from about 8 wt % to about 31 wt %. Aluminum, silicon, boron, titanium, and other hardness enhancing materials may also be present. Hot investment casting may be used to form items from the alloys, which may then be shaped or polished to a final form. Annular finger rings constructed from these materials may have a white appearance similar to white gold or platinum, may have increased resistance to scratching compared to traditional cobalt chromium rings, and may be easily be removed by cracking in an emergency situation.
1 . A method of forming a jewelry article comprising a finger ring from a cobalt chromium alloy, wherein the method comprises:
forming blend comprising:
about 43 wt % to about 50 wt % cobalt;
about 27 wt % to about 32 wt % chromium;
about 12 wt % to about 16 wt % molybdenum; and
at least one hardness enhancing element;
melting the blend to form a molten alloy;
shaping the molten alloy into a rough desired shape by placement in a mold;
cooling the molten alloy to provide a hardened part; and
forming the hardened part into a shape of a finger ring;
wherein the finger ring has a surface hardness of at least about 45 HRC; and
wherein the finger ring is configured to break upon application of a force less than about 500 lbf to at least two points on an outside surface of the finger ring.
2 . The method of claim 1 , wherein shaping the molten alloy comprises hot investment casting.
3 . The method of claim 1 , wherein the at least one hardness enhancing element comprises aluminum, silicon, boron, titanium, iron, nickel, zirconium, cerium, lanthanum, carbon, manganese, or a combination of any of the foregoing.
4 . The method of claim 1 , wherein the surface hardness is at least about 55 HRC.
5 . The method of claim 1 , wherein the surface hardness is from about 50 HRC to about 70 HRC.
6 . The method of claim 1 , wherein the cobalt chromium alloy comprises greater than about 90 wt % cobalt, chromium, and molybdenum combined.
7 . The method of claim 1 , wherein the force is from about 311 lbf to about 499 lbf.
8 . The method of claim 1 , wherein the cobalt chromium alloy comprises from about 0.5 wt % to about 10 wt % of the at least one hardness enhancing element.
9 . The method of claim 1 , wherein the hardness enhancing element comprises up to but not more than about 3 wt % each of carbon, nickel, and manganese.
10 . The method of claim 1 , wherein,
the at least one hardness enhancing element comprises more than one hardness enhancing element; and
the cobalt chromium alloy comprises from about 0.5 wt % to about 3 wt % of each of the more than one hardness enhancing element.
11 . A method of forming a jewelry article comprising a finger ring from a cobalt chromium alloy, wherein the method comprises:
forming a blend comprising:
about 35 wt % to about 65 wt % cobalt;
about 16 wt % to about 20 wt % chromium;
about 26 wt % to about 31 wt % molybdenum; and
at least one hardness enhancing element;
melting the blend to form a molten alloy;
shaping the molten alloy into a rough desired shape by placement in a mold;
cooling the molten alloy to provide a hardened part; and
forming the hardened part into a shape of a finger ring;
wherein the finger ring has a surface hardness of at least about 45 HRC; and
wherein the finger ring is configured to break upon application of a force less than about 500 lbf to at least two points on an outside surface of the finger ring.
12 . The method of claim 11 , wherein shaping the molten alloy comprises hot investment casting.
13 . The method of claim 11 , wherein the at least one hardness enhancing element comprises aluminum, silicon, boron, titanium, iron, nickel, zirconium, cerium, lanthanum, carbon, manganese, or a combination of any of the foregoing.
14 . The method of claim 11 , wherein the surface hardness is at least about 55 HRC.
15 . The method of claim 11 , wherein the surface hardness is from about 50 HRC to about 70 HRC.
16 . The method of claim 11 , wherein the cobalt chromium alloy comprises greater than about 90 wt % cobalt, chromium, and molybdenum combined.
17 . The method of claim 11 , wherein the force is from about 311 lbf to about 499 lbf.
18 . The method of claim 11 , wherein the cobalt chromium alloy comprises from about 0.5 wt % to about 10 wt % of the at least one hardness enhancing element.
19 . The method of claim 11 , wherein the hardness enhancing element comprises up to but not more than about 3 wt % each of carbon, nickel, and manganese.
20 . The method of claim 11 , wherein,
the at least one hardness enhancing element comprises more than one hardness enhancing element; and
the cobalt chromium alloy comprises from about 0.5 wt % to about 3 wt % of each of the more than one hardness enhancing elements.
21 . A method of forming a jewelry article comprising a finger ring from a cobalt chromium alloy, wherein the method comprises:
forming a blend comprising:
about 35 wt % to about 65 wt % cobalt;
about 17 wt % to about 21 wt % chromium;
about 8 wt % to about 12 wt % molybdenum; and
at least one hardness enhancing element;
melting the blend to form a molten alloy;
shaping the molten alloy into a rough desired shape by placement in a mold;
cooling the molten alloy to provide a hardened part; and
forming the hardened part into a shape of a finger ring;
wherein the finger ring has a surface hardness of at least about 45 HRC; and
wherein the finger ring is configured to break upon application of a force less than about 500 lbf to at least two points on an outside surface of the finger ring.
22 . The method of claim 21 , wherein shaping the molten alloy comprises hot investment casting.
23 . The method of claim 21 , wherein the at least one hardness enhancing element is selected from aluminum, silicon, boron, titanium, iron, nickel, zirconium, cerium, lanthanum, carbon, manganese, and a combination of any of the foregoing.
24 . The method of claim 21 , wherein the at least one binder is selected from iron, carbon, nickel, manganese, and a combination of any of the foregoing.
25 . The method of claim 21 , wherein the surface hardness is at least about 55 HRC.
26 . The method of claim 21 , wherein the surface hardness is from about 50 HRC to about 70 HRC.
27 . The method of claim 21 , wherein the cobalt chromium alloy comprises greater than about 90 wt % cobalt, chromium, and molybdenum combined.
28 . The method of claim 21 , wherein the force is from about 311 lbf to about 499 lbf.
29 . The method of claim 21 , wherein the cobalt chromium alloy comprises from about 0.5 wt % to about 10 wt % of the at least one hardness enhancing element.
30 . The method of claim 21 , wherein the hardness enhancing element comprises up to but not more than about 3 wt % each of carbon, nickel, and manganese.
31 . The method of claim 21 , wherein,
the at least one hardness enhancing element comprises more than one hardness enhancing element; and
the cobalt chromium alloy comprises from about 0.5 wt % to about 3 wt % of each of the more than one hardness enhancing elements.