Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Effects of Heat Treatment and Hot Forging on Microstructure and Mechanical Properties of Co-Cr-Mo Alloy for Surgical Implants
Yoshimitsu Okazaki
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2008 Volume 49 Issue 4 Pages 817-823


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, M23C6 carbides precipitated along the grain boundary in the γ phase matrix containing a small amount of ε phase. The 0.2% proof strength (σ0.2%PS), ultimate tensile strength (σUTS), 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 σ0.2%PS and σUTS 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 σ0.2%PS, σUTS, 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 M23C6 carbide and a small amount of M6C 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.

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© 2008 The Japan Institute of Metals and Materials
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