18K Ni-FREE AGE HARDENABLE WHITE GOLD ALLOY

Abstract

The present invention is directed to a reduced-cost 18K white gold alloy that is Ni-free, and otherwise contains a low w % of precious metals, including about 7 w % palladium, exhibits a color which is considered white, and shows age hardening characteristics commensurate with nickel containing 18 Karat gold alloys.

1 . A gold-based nickel-free alloy composition comprising:
 about 75% gold,   about 6-7% palladium,   about 10% copper, and   2-5.5% zinc;   wherein said composition exhibits a color which is considered white, and shows age hardening characteristics commensurate with nickel containing 18 Karat gold alloys.   
     
     
         2 . The composition of  claim 1  further comprising about 3% silver. 
     
     
         3 . The composition of  claim 1  further comprising about 5% silver. 
     
     
         4 . The composition of  claim 1 , wherein the age hardness as cast exceeds 155 vickers. 
     
     
         5 . The composition of  claim 1 , wherein the age hardness as cast exceeds 175 vickers. 
     
     
         6 . The composition of  claim 1 , wherein the age hardness increases by at least 50 vickers when heated. 
     
     
         7 . The composition of  claim 1  wherein color components L*, *, and b* are in the ranges of 80-84, 2-2.5, and 12.75-13, respectively. 
     
     
         8 . The composition of  claim 1 , wherein the YI value is in the range of 28.7-29.3. 
     
     
         9 . The composition of  claim 1 , wherein said composition is used for jewelry. 
     
     
         10 . The composition of  claim 9 , wherein said composition is absent any rhodium plating.