Study on the effect of preheating temperature of SLM process on characteristics of CoCrMo alloy

Abstract

This is a study on the effects of the pre-heating temperature of the selective laser melting (SLM) process on the microstructure and mechanical characteristics of CoCrMo alloy specimens. Specimens were created using 36 process conditions at pre-heating temperatures of 50, 100, and 150 °C, and high-density process conditions with 99.99% density or higher were presented. The changes of characteristics such as microstructure, mechanical characteristics, and residual stress were observed according to pre-heating temperature. The phase transformation from FCC α -Co phase to martensitic ε-Co phase was inhibited because the cooling speed increased as the pre-heating temperature increased. And that was caused the coarse grain of alpha phase. In addition, elongation properties were improved because the FCC α-Co phase acted as a deformation mechanism as the martensitic ε-Co phase decreased; however, strength was only minimally reduced because the ε-Co phase of the nano scale formed an orientation relationship. Consequently, the cooling speed increased as the pre-heating temperature increased (50 °C → 150 °C), which inhibited the α-Co phase → martensitic ε-Co phase transformation, resulting in decreased residual stress and improved mechanical characteristics.