Hot Compression Behavior and Hot Processing Map of CoCrMo Alloy Prepared by Vacuum Induction Melting-Electroslag Remelting

Abstract

The hot compression behavior of cast CoCrMo alloy prepared by vacuum induction melting-electroslag remelting duplex process is systematically explored under the conditions of temperature range of 950 ∼ 1150 °C and strain rate of 10⁻² s⁻¹∼ 10 s⁻¹. Through the analysis of true stress-strain curve, it is found that the increase of deformation temperature can significantly reduce the flow stress (the peak stress at 1150 °C and 10⁻² s⁻¹.is nearly 70% lower than that at 950 °C and 10⁻² s⁻¹.), and the strain rate sensitivity index m fluctuates in the range of 0.1 ∼ 0.34, showing the coexistence characteristics of dynamic recrystallization and hot working instability. Based on Arrhenius constitutive equation and power dissipation theory, the hot working diagram of cast CoCrMo alloy is constructed, and its safe machining domain (temperature ≥ 1050 °C, strain rate ≤ 1 s⁻¹.) and instability region (temperature ≤ 1000 °C, strain rate ≥ 3 s⁻¹.) are defined. The critical condition of instability corresponds to the peak dissipation efficiency of 40%. The research results provide a direct theoretical basis for optimizing the process parameters of casting CoCrMo alloy forging and blanking and avoiding hot working defects, and have engineering guidance value for improving the quality of medical implants and aerospace parts blanks.