Effects of heat treatment on microstructure and performance of NiCr/Cr3C2-WS2 composite coatings

The NiCr/Cr3C2-WS2 high-temperature self-lubrication wear-resistant composite coatings were fabricated on substrate of austenitic stainless steel by laser cladding. The high-temperature structural stability of the composite coatings was evaluated by aging at 600°C for 10 h, 30 h, 50 h, respectively, and the microstructure of the as-laser clad and aged coatings was examined by means of XRD, SEM, EDS. The sliding wear resistance of the as-laser and aged coatings was evaluated at 600°C. The results show that the γ-(Fe, Ni)/Cr7C3 eutectic phase, Cr7C3 hard phase and CrS/WS2 phase all exist in the as-laser clad and aged coatings. The volume fraction of eutectic phases reduces gradually with the increasing of aging time due to their dissolution. The microhardness of the aged coating decreases slightly after aging at 600°C for 50 h due to the dissolution of the eutectic phases and notable breaking or granulation of the Cr7C3 phases aging for 50 h, but the fractional properties are not significantly affected by heat treatment.