Formation of novel graded interface and its function on mechanical properties of WC1−x reinforced Inconel 718 composites processed by selective laser melting

•Densification and microstructure of SLM-processed samples were disclosed.•Novel graded interfacial layer structure surrounded with a diffusion layer was found.•Formation mechanism of the novel layer structure was researched.•A comprehensive relationship between microstructure and wear performance was explained.

Selective laser melting (SLM) additive manufacturing (AM) process was applied to produce WC1−x particle reinforced Inconel 718 composite parts. The effects of the applied laser energy linear density (η) on the densification behavior, particle distribution state and the microstructure of the WC1−x/Inconel 718 composite parts were deeply researched in this paper. According to the experimental results, a η of 303 J/m resulted in a nearly full dense part with a uniform distribution of the WC1−x reinforcing particles owing to sufficient melting of mixed powder and rearrangement of the WC1−x particles. Due to an in situ reaction between the reinforcing particle surfaces and Inconel 718, a graded interfacial layer with a composition of (W, M)C3 (M = Ni, Cr, Fe) was tailored between the reinforcing particles and the matrix during the SLM processing. Meanwhile, a category of diffusion layer between the graded interfacial layer and the matrix with a composition of (W, M)C2 (M = Ni, Cr, Fe, Nb) was found, showing a slight increase amount of Ni, Cr, Fe and decrease of W and C as well as an additional strong carbide-forming element Nb. At an optimal η of 242 J/m, a considerably high microhardness of 389.4 HV0.1 and a considerably low coefficient of friction (COF) of 0.39 and resultant low wear rate of 2.3 × 10−4 mm3 N−1 m−1 were realized due to the united strengthening of the graded interfacial layer and the (W, M)C2 diffusion layer. A comprehensive relationship between densification behavior, microstructure and wear performance of the SLM-processed WC1−x/Inconel 718 composite parts was discussed.