Potential of the Co-Cr-Ni-Nb as a dental alloy system

H. Mohammed-Al Tahawi, DDS,MScD,PhD,FICD,DICOI,FADM
College of Dentistry, King Saud University, P.O. Box 60169, Riyadh 11545, Saudi Arabia  

Fourteen quarternary Co-Cr-Ni-Nb alloys were prepared maintaining a constant Co:Cr:Ni and varying the concentration of Nb from 0-20%. Four tensile testing specimens of each alloy composition were cast and tested, The ternary alloy possessed a yield strength (YS) of 44X10³ psi and elongation of 29%. Contrary to Ta, the addition of up to 3% Nb had little effect on strength (YS 45X10³, UTS 79X10³ psi). Ductility remained rather constant (25%). Concentrations up to 6% Nb caused mild increase in strength (YS45X10³, UTS 80X10³ psi) and substantial decrease in elongation (5.9%). An equivalent amount of Ta raised YS to 74X10³, UTS to 106X10³, and reduced elongation to 21%. Deterioration of elongation with minimal gain in strength continued with increasing Nb. At concentrations higher than 6% an eutectic was observed. Higher concentrations caused large amounts of both sigma and the brittle eutectic. The alloys produced by adding Nb lacked both strength and ductility necessary for dental applications.

Saudi Dental Journal 1989;1(1):8-13.