Effect of laser power on microstructure and interfacial bonding strength of laser cladding 17-4PH stainless steel coatings

Abstract 17-4PH stainless steel coatings is widely used in the field of laser repair due to its excellent performance. In the service process, the coatings not only have excellent mechanical properties but also ensure the formation of an excellent metallurgical bond between the coatings and the substrate. In this paper, the formability, microstructure evolution, texture characterization, microhardness and interface bonding strength of laser cladding 17-4PH stainless steel coatings under different laser powers are studied. A novel test method and related fixture are designed to analyze the interface fracture behavior of T-shaped specimens and evaluate the bonding strength. The relationship between microstructure and interfacial bonding strength of T-shaped specimens is investigated by electron backscattering diffraction (EBSD) and a universal testing machine. The higher stress concentration at the interface and heat-affected zone has been found by comparing the coatings. When the laser power is 2200 W, the microhardness and interfacial bonding strength are higher than other specimens, which are 450 HV and 908 MPa, respectively. This phenomenon is due to the appropriate laser power refines grains and reduces micro defects at the interface, which all contribute to improving the interfacial bonding strength. Fracture analysis shows that the combination of microvoids and unmelted powder contributed to accelerating the propagation of cracks.