Effects of various heat treatments on microstructure and mechanical properties of investment cast Co-Cr-Mo implants
Abstract
In this study, the effects of various heat treatments (solutionizing, solutionizing + aging) on the microstructure and mechanical properties of the Co-Cr-Mo based hip implants produced by investment casting were investigated. The solution treatments were carried out at 1125°C, 1175°C and 1225°C for 3 hours under argon atmosphere. The aging treatments were carried at 850°C for 4 hours. The samples were examined under scanning electron microscope (SEM) and optical microscope (OM). Room temperature tensile tests and hardness tests were applied. The results showed that, the process of solutionizing at 1175°C and subsequent aging resulted in the formation of the smallest size precipitates with more homogeneous distribution in the interdendritic space of the as-cast structure compared to other treatments. According to tensile test results of the aged samples, as the solutionizing temperature increased to 1175°C both strength and elongation values increased. However, with the increase of solutionizing temperature to 1225°C, strength and elongation values decreased again. Solutionizing temperature of 1175°C gave the best microstructure-mechanical property relationship. Moreover, hardness values increased with the subsequent aging, yet do not change significantly with the solutionizing temperature.
Keywords
solutionizing, aging, investment casting, hip implant, mechanical properties
Thanks
This work would not have been possible without the support of the Mr. Önder ERTÜRKAN and the Ortopedya Implant A.Ş. company for helping and providing for the work. We would especially like to thank for their support during our study.
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