DIFFUSION BONDING OF DISSIMILAR METALS USING DIFFERENT INTER-LAYERS

Abstract

Diffusion bonding is a solid state joining process which is mainly used for joining of similar and dissimilar metals. It has been gaining greater attention in aerospace and nuclear industries. In this study, diffusion bonding of 304L stainless steel and mild steel was done by conventional method, and a new approach named impulse pressure diffusion bonding. A copper interlayer was also introduced as an interlayer to reduce the micro voids and to improve the joint performance of the diffusion bonds. Bonding temperature, pressure and time were considered as three important input process parameters. The diffusion bonding was performed at 850- 950 ºC with step of 50 for a constant time of 30 min. Scanning electron microscope and energy dispersive spectrometry elemental analysis was done to analyze the interface. It was found that the diffusion of the copper occurred across the bond interface. Tensile test and micro hardness were performed in order to determine the strength of the joint. The highest tensile strength achieved in diffusion bonding process with interlayer is 464.40 MPa at 900 ºC, 15 MPa and 30 min bonding time. The highest tensile strength in impulse pressure diffusion bonding is 555.34 MPa at 950 ºC, (15-7.5) MPa and 30 min bonding time. Hardness of the diffusion bonds follows the same pattern having lowest value (115 HV) at diffusion bond interface.