Fatigue behavior of biomedical Co–Cr–Mo–W alloy fabricated by selective laser melting

Co–Cr–Mo based alloy was widely used biomaterials for metallic implants fields. Recently, selective lase melting (SLM), one of the additive manufacturing technologies, is broadly studied because it can produce metallic implants with complex geometries and high degree of personalization. However, the possibility of mechanical failure must be avoided during the working period of SLM produced biomaterials. Therefore, in this paper we investigated the fatigue behaviors of the SLM Co–Cr–Mo–W alloy and their corresponding microstructure and fracture morphology. The sand mold casting fabricated (Cast) Co–Cr–Mo–W alloys with the same chemical composition as SLM specimens were also investigated and compared. The results showed that the SLM Co–Cr–Mo–W alloy exhibits higher fatigue life, tensile strength, and ductility than Cast Co–Cr–Mo–W alloy. The high fraction of Σ3 boundaries and precipitates in SLM Co–Cr–Mo–W alloy lead to secondary cracks and deflected fatigue crack path, which can alleviate the stress concentrations of the main fatigue cracks and decrease the fatigue crack growth rate. However, the dendritic structure of Cast Co–Cr–Mo–W alloy cause cleavage fracture mode and the large island-like precipitates can generate stress concentration, which result in lower fatigue life. We believed that the results of this work can provide a new perspective towards microstructure regulation for additive manufacturing technology and paved way for in-depth application of SLM fabricated biomedical alloy.