Nickel-free white gold alloy compositions with reversible hardness characteristics
View Patent ↗A nickel-free white gold alloy composition having selectively reversible hardness characteristics between its annealed- and aged-hardness values, consists essentially of: about 55–60% gold; about 6.0–10.0% palladium; about 5.0–12.0% copper; about 0.1–2.0% zinc; and about 20–30% silver. A 14-karat nickel-free white gold alloy composition, consists essentially of: about 58.5% gold; about 25.0–27.15% silver; about 6.0% palladium; about 5.0–12.0% copper; about 0–2.0% zinc; about 0–0.2% cobalt; about 0–0.005% iridium; and about 0–0.01% lithium.
1. A 14-karat nickel-free white gold alloy composition, consisting essentially of:
about 58.5% gold;
about 27.15% silver;
about 6.0% palladium;
about 7.635% copper;
about 0.5% zinc;
about 0.2% cobalt;
about 0.005% iridium; and
about 0–0.01% lithium.
2. A 14-karat nickel-free white gold alloy composition as set forth in claim 1 wherein said composition has a Grade 3 Off-White color, as defined by the White Gold Task Force.
3. A 14-karat nickel-free white gold alloy composition as set forth in claim 2 wherein said composition has a yellowness index (YI) of about 31.
4. A 14-karat nickel-free white gold alloy composition as set forth in claim 1 wherein said composition is capable of an annealed-hardness value of about 140 VEN by heating to about 700–800° C. for about 1 hour and quenching in water at room temperature.
5. A 14-karat nickel-free white gold alloy composition as set forth in claim 1 wherein said composition is capable of an aged-hardness value of about 245 VHN by heating to a temperature of about 400° C. for about 1–4 hours in a protective atmosphere to prevent oxidation.
6. A 14-karat nickel-free white gold alloy composition as set forth in claim 1 wherein the ness of said composition is selectively reversible between its annealed- and aged-hardness values.
7. A 14-karat nickel-free white gold alloy composition as set forth in claim 1 wherein said composition has a melting point of less than about 1100° C.