Effect of material anisotropy and heat treatment on machinability of TiC/CM247LC nickel-based composite fabricated by selective laser melting

Additively manufactured CM247LC nickel-based superalloy exhibits significant application potential in the aerospace field. However, serious problems of high crack sensitivity, poor surface quality and low dimensional accuracy are greatly limiting its application and development. Adding nanoparticles for preparation and post-treatment, including heat treatment and machining, have become effective methods to solve the above drawbacks. In this paper, TiC/CM247LC nickel-based composite was prepared by selective laser melting (SLM), and a solid solution + aging heat treatment was employed to improve the comprehensive properties. The as-built and heat-treated composites were initially analyzed for surface morphology, roughness, microstructure and microhardness. The effect of material anisotropy and heat treatment on the machinability of the composite was systematically investigated. The results indicated that the cutting force exhibits significant anisotropic characteristics impacted by the microstructure and mechanical properties. After heat treatment, the synergistic strengthening effect induced by the γ' phase resulted in the maximum cutting force appearing on the XOZ plane. Compared with the as-built samples, the relatively poor surface quality of the heat-treated samples is attributed to the synergistic strength-toughness effect induced by the γ′ phase and the hindrance of carbide phase to dislocations. The microhardness of the surface layer is significantly enhanced after milling, and the higher microhardness of the XOZ plane and the heat-treated samples is dominated by the fusion boundary and γ′ phase. Moreover, the differences in serrated edges and extrusion stripes of different samples are correlated with the strengthening and toughening induced by γ′ phase. This study can provide guidance for regulating the material properties and machinability of AMed superalloys.