Effect of Heat Treatment on Microstructure and Mechanical Properties of Ni- and C-Free Co--Cr--Mo Alloys for Medical Applications

The effect of pre-heat treatments, followed by a hot forging process, on the microstructure and strength of Co–Cr–Mo alloys was investigated. Four pre-heat treatments were conducted at 1170, 1200, 1230 and 1260 C for three different time condition: 2, 6 and 15 h and then water cooled to room temperature. Tensile tests and XRD analyses were carried out on both as-cast alloy and heat-treated alloys. The volume fraction of retained phase increases with increasing the heat treatment temperature, suggesting that the ! " martensitic transformation is suppressed by a higher temperature heat treatment. Tensile strength slightly decreases with increasing the heat treatment temperature and the heat treatment time, whereas the ductility slightly increases. The phase completely dissolves into matrix when the alloy is heat-treated at 1260 C for longer than 6 h.