Influence of Heat Treatment on Microstructure and Mechanical Properties of Laser Cladding Coatings

Abstract

This study investigates the influence of various heat treatment processes on the microstructure and properties of laser cladding Fe314 coatings. The microstructure, phases, and impact fracture morphology of the cladding layer were observed using X-ray diffraction and scanning electron microscopy, among other methods. The hardness and impact performance of the cladding layer were also tested. The results indicated that there was compositional segregation and non-equilibrium microstructure in the untreated cladding layer, with an average microhardness of 368.67 HV and an impact toughness of 27 J, exhibiting quasi-cleavage fracture. The stress-relief annealing treatment resulted in a uniform distribution of M23C6 carbides inside the cladding layer. The pinning effect generated by M23C6 reduced the microhardness by 16.26% and increased the impact toughness to 54 J. The impact fracture surface exhibited ductile fracture. After secondary normalizing and annealing, the microstructure of the cladding layer transformed into a fine single-phase austenite structure, and fine M7C3 carbides precipitated at the grain boundaries. Under the effects of fine grain strengthening and dispersion strengthening, the microhardness of the cladding layer decreased by 38.14%, and the average impact absorbed energy of the specimen was 64 J, showing complete ductile fracture.