Microstructure and Tribological Behaviour of Inconel-625 Superalloy Produced by Selective Laser Melting

This research discusses the comparative investigation of the Inconel-625 superalloy manufactured by Selective Laser Melting (SLM) process and conventional process. The fabricated component was investigated to reveal the phase transformations, microstructural features and nano-hardness. Further, wear test was conducted on specimens manufactured by both the methods as above, to study the tribological properties. XRD analysis showed that the SLM specimen has more intensity at (111) diffraction peak than the other two specimens and that the solid solution of γ-(Ni, Cr, Fe) (FCC) phases grew at (111), (2 0 0) and (220) planes. The Inconel-625 powder had lattice parameters 0.3592 nm, 0.3116 nm and 0.3012 nm, whereas the SLM specimen possessed the lattice parameters 0.3599 nm, 0.3121 nm and 0.3012 nm which were higher than the other two specimens. The microstructure analysis confirmed the presence of consistent and homogeneously equiaxed cell in the conventional alloy, whereas the SLM specimen possessed heterogeneous columnar structure. Along with the columnar cell, some equiaxed and cellular cell were also formed in the SLM specimen due to remelting of the overlapped region. Moreover, the formation of equiaxed cell in XY, YZ and ZX plane directions of the conventional alloy specimen and columnar cell in the SLM specimen was confirmed through Electron backscatter diffraction (EBSD) analysis. The SLM-produced specimen exhibited higher nano-hardness due to the formation of angular columnar cell, fine hard phases, effective bonding strength and defect-free surface. Abrasive wear mechanism played an important role in both the samples. The wear rate of the conventional Inconel-625 alloy specimen was around 4.58 × 10^–3 mm³/m while it was 1.83 × 10^–3 mm³/m. The worn-out surface of the SLM specimen produced a lower roughness average compared with the conventional Inconel-625 specimen. Thus, the SLM technique is a promising and predominant technique to develop nickel-based superalloys for frictional applications.