Formation mechanisms of high quality diffusion bonded martensitic stainless steel joints

Diffusion bonding of martensitic stainless steel was conducted at different times. Based on the interface characteristic and shear strength, bonding mechanisms were discussed. Results showed that the bonding quality was controlled by void shrinkage and interface grain boundary migration. Large voids with scraggly edges changed to small voids with smooth edges, leading to an increase in interface bonding ratio. Two cases of interface grain boundary migration were revealed: interface grain boundary migration at the triple junction induced by the reduction in grain boundary energy and strain induced interface grain boundary migration resulted from the stored energy. Owing to the void shrinkage and interface grain boundary migration, the shear strength of the joint matched that of the base material.