In-situ manipulating microstructure of CoCrMo alloy using selective laser melting with a novel scanning strategy

Abstract

Three types of distinct dense microstructure, namely narrow columnar grains, nearly equiaxed refined grains, and duplex ε + γ microstructure, can be in-situ fabricated using a novel laser scanning strategy. The strategy includes a melting scanning with the laser energy density of 2∼26 J/mm3 to refine the microstructure and multiple non-melting scanning with an extremely low laser energy density of 0.9∼1.8 J/mm3 to produce a large amount of ε-martensite in the γ austenite matrix. As a result, an exceptionally high tensile strength of 1,503 MPa, outstanding ductility of 18%, and improved hardness of 502 HV can be achieved through additional scanning with appropriate energy density. This work demonstrates that the microstructure of selected laser melted alloy can be in-situ manipulated to tune mechanical properties.