Effect of cryogenic treatment on tribological behavior of Ti6Al4V alloy fabricated by selective laser melting

Abstract Ti6Al4V fabricated by selective laser melting (SLM) is commonly used as an artificial hip joint. However, the inferior tribological properties fall far short of the requirements for biomedical engineering and is harmful to the patients. In this study, cryogenic treatment (CT) was proposed to solve this problem. CT at -196 °C with a soaking time of both 2 h and 72 h were conducted, and their tribological properties were investigated by microstructure observation, Vickers hardness, and wear tests. The results showed that the microstructure of the as-fabricated and cryogenic treated (CTed) for 2 h are mainly composed of acicular martensite (α' phase). However, the microstructure is transformed into alpha and beta phases after CT for 72 h. Vickers hardness of the specimens as-fabricated, CTed for 2 h and 72 h are 390.79 HV, 388.03 HV, and 371.34 HV, respectively. CT induces a significant improvement in tribological properties, which is correlated with the microstructure evolution. A similar wear mechanism can be observed for the specimens as-fabricated and CTed for 2h, which is the co-action of severe abrasive wear, adhesive wear, and fatigue wear. While the specimen CTed for 72h is slight abrasive wear mechanism.