Effects of Heat Treatment and Hot Forging on Microstructure and Mechanical Properties of Co-Cr-Mo Alloy for Surgical Implants

摘要

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 deg C for 1 h, M23C6 carbides precipitated along the grain boundary in the gamma phase matrix containing a small amount of delta phase. The 0.2 parcent proof strength (sigma_0.2 percent ps), ultimate tensile strength (sigma_UTS), total elongation (T. E.), and reduction of area (R. A.) of annealed alloy were 553 +- 2MPa, 928 +- 41 MPa, 21 +- 2 percent, and 15 +- 1 percent, respectively. The sigma_0.2 percent PS and sigma_UTS of the Co-Cr-Mo alloy hot-forged at a starting temperature of 1100 deg C increased linearly with an increase in reduction in area, whereas T. E. gradually decreased with an increase in the reduction. The sigma_(0.2 percent PS), sigma(_UTST), T.E., and R. A. of 57 percent hot-forged alloy were 715 +- 86MPa, 1109 +- 61 MPa, 8 +- 1 percent , and 10 +- 1 percent, respectively. In the 57 percenr hot-forged Co-Cr-Mo alloy, a large amount of M_23C_6 carbide and a small amount of M_6C carbide were observed in the gamma phase matrix containing the epsilon phase. In the light of these results, it appears that hot forging with a starting temperature of approximately 1100 deg C provided excellent mechanical properties to the alloys.