High-strength stainless steel joints achieved by co-regulation mechanism of phosphide dispersed distribution and γ-phase generation

A novel iron-based filler FeCr18Ni10Si6P6 was designed to address the inherent limitations of joint strength reduction caused by the formation of the continuous brittle phase in the diffusion affected zone (DAZ) during traditional iron-based filler joints. The influence of process parameters on the microstructure evolution and mechanical properties of the joints was subjected to a comprehensive examination. The results indicated that the diffusion of Cr would result in the formation of α-phase in DAZ of the joints, which predominantly solidified most of the P atoms. This ultimately led to the precipitation of phosphide in the form of fine needles, enhancing the strength of the joints and altering the joint fracture region from DAZ to athermal solidified zone (ASZ). The joint strength peaked at 177 MPa when brazed at 1120 °C for 15 min, which is 2.6 times higher than that of traditional iron-based filler metals used in bonding. This filler metal presents a novel approach to the low-cost and high-quality joining of stainless steel.