Mechanical Performances and Failure Modes of Direct Diffusion Bonding Joints of 316L Stainless Steel

Abstract

Direct diffusion bonding of 316L stainless steel was performed at 850-1100°C for 1-3 h under a pressure of 10MPa in this study. The effect of bonding temperature and holding time on mechanical performances of the joints was investigated. Tensile tests were conducted to evaluate strength and elongation of the joints at room temperature and elevated temperature of 550°C. The microstructure and fracture surfaces of the joints were examined by optical microscope (OM) and scanning electronic microscope (SEM). The results indicated that the elongation of the joints increased with the increase of bonding temperature and holding time. However, overlong holding time had a side effect on the strength of the joint. Moreover, the change of the mechanical properties was closely related to the variation of the microstructure of the joints. The X-ray diffraction (XRD) analysis revealed that FeCr and Fe0.64Ni0.36 were formed at the DB6 joint during bonding process. It is suggested that FeCr should be detrimental to the improvement of high temperature strength of the joint.