18Ni300/Inconel 625 alloy gradient materials fabricated by directed energy deposition

Functionally graded materials (FGMs) exhibit high fusion, which offer a potential solution to the issue of performance degradation caused by the inconsistency of thermal expansion coefficient and elastic modulus of different materials. As an advanced additive manufacturing method, directional energy deposition is widely used in the preparation of FGMs. This work focuses on characterizing the microstructure and compressive strength of 18Ni300/Inconel 625 gradient materials with varying composition ratios in the as-built state, prepared using powder directed energy deposition technology. The microstructure of the 18Ni300/Inconel 625 gradient materials includes columnar grains and cellular grains, and the phase mainly includes martensite (alpha-Fe) and gamma-Ni. FGMs have a maximum hardness of 348 HV0.2 and a minimum coefficient of friction of 0.2588. Compared with the single materials, the mechanical compression performance of the gradient materials were basically consistent in three different orientations, with a maximum compression modulus of 3165.14 MPa of OD orientation. The average compressive moduli of FGMs is 2957.89 Mpa. The design and preparation of high-performance functionally graded materials provides an in-depth mechanistic understanding of improving the fusion of different materials.