Morphology and properties of CoCrMo parts fabricated by selective laser melting

Abstract

Due to the rapid melting and solidification mechanisms involved in selective laser melting (SLM), CoCrMo alloys fabricated by SLM differ from the cast form of the same alloy. In this study, the surface morphologies, enhancement of mechanical properties and change to microstructure by heat treatment were discussed. Results showed that the microstructure of sample fabricated by SLM consisted mainly of face-centered-cubic (FCC) cobalt-rich solid solutions and carbide scattered cobalt-rich solid solutions, where Cr and Mo were dissolved in the Co-base phase and M23C6. The carbide scattered Co-base phase existed in the form of even margins. The tensile fracture of SLM-fabricated parts was mostly quasi-cleavage brittle fracture. Heat treatment transformed the SLM-fabricated parts such that failure occurred through ductile rather than brittle fracture, causing an increase in the tensile strength and elongation of the SLM-fabricated parts in addition to reduced yield strength and hardness. Some annealing twins were formed after heat treatment, which were demonstrated by TEM. These results will contribute to the development of biomedical CoCrMo alloys fabricated by SLM.