Effects of Heat Treatment and Hot Forging on Microstructure and Mechanical Properties of Co-Cr-Mo Alloy for Surgical Implants
The effects of heat treatment and hot forging on the microstructure and mechanical properties of Co-Cr-Mo alloy for implant applications were examined. In an alloy annealed at 1200°C for 1 h, M<SUB>23</SUB>C<SUB>6</SUB> carbides precipitated along the grain boundary in the γ phase matrix containing a small amount of ε phase. The 0.2% proof strength (σ<SUB>0.2%PS</SUB>), ultimate tensile strength (σ<SUB>UTS</SUB>), total elongation (T. E.), and reduction of area (R. A.) of annealed alloy were 553±2 MPa, 928±41 MPa, 21±2%, and 15±1%, respectively. The σ<SUB>0.2%PS</SUB> and σ<SUB>UTS</SUB> of the Co-Cr-Mo alloy hot-forged at a starting temperature of 1100°C increased linearly with an increase in reduction in area, whereas T. E. gradually decreased with an increase in the reduction. The σ<SUB>0.2%PS</SUB>, σ<SUB>UTS</SUB>, T. E., and R. A. of 57% hot-forged alloy were 715±86 MPa, 1109±61 MPa, 8±1%, and 10±1%, respectively. In the 57% hot-forged Co-Cr-Mo alloy, a large amount of M<SUB>23</SUB>C<SUB>6</SUB> carbide and a small amount of M<SUB>6</SUB>C carbide were observed in the γ phase matrix containing the ε phase. In the light of these results, it appears that hot forging with a starting temperature of approximately 1100°C provided excellent mechanical properties to the alloys.
- Materials transactions
Materials transactions 49(4), 817-823, 2008-04-01