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.