Effect of heat treatment on microstructure and mechanical properties of Fe60 coating by laser cladding on 304 stainless steel

Abstract

Heat treatment has a direct effect on the microstructure and mechanical properties of laser cladding coatings. To investigate the influence of heat treatment on the microstructure and mechanical properties of Fe60 coating, the surface of 304 stainless steel was coated with Fe60 coating by laser cladding technology, and then normalizing treatments were conducted on the coatings at temperatures of 950 °C, 1000 °C, and 1050 °C, as well as a solution treatment at 1050 °C. The microstructure and phase composition of the coatings before and after heat treatment were analyzed using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffractometry (XRD). In addition, the microhardness, tensile properties, and impact toughness of the coating were evaluated through experimental testing. Furthermore, SEM examination was performed to observe the tensile fracture morphology with subsequent analysis. The results show that no phase transition occurs in the coatings after heat treatment. Subsequent to normalizing treatments, the grains are gradually refined with the increase of normalizing temperature. Solution treatment leads to grain refinement in the coating and significantly eliminates precipitated phases. The heat treatment effectively reduces residual stress and lattice distortion in the coating, which reduces the microhardness and significantly improves tensile properties and impact resistance at the same time. Observation of the tensile fracture microstructure reveals ductile dimple fractures in the substrate and brittle cleavage fractures within the coated region. The results can provide a valuable reference for enhancing the mechanical properties of Fe60 coatings by laser cladding.