Difffusion bonding of non weldable high alloy steel

Abstract

Diffusion bonding is a viable joining process which could minimize the weldability related problems of high Mn steel. The steel used for the present investigation is a twinning induced plasticity (TWIP) high alloy steel containing 23 Mn, 4 Si and 3% Al. The diffusion bonding of TWIP steel was carried out after Ni coating of joining surface. The diffusion bonding process was carried out in high vacuum hot press at 700, 800 and 900°C for 120 minutes under uniaxial load of ~25MPa. The detailed microstructural analysis and elemental distribution across the joint was carried out using optical microscopy and electron probe microanalysis (EPMA). The EPMA analysis showed that the diffusion bonding was favored by the large scale inter-diffusion of Ni and Mn through the ferrite phase in TWIP steel. The elemental mapping of the joint processed at 900°C revealed that maximum wt. % of Ni at any point is ≤ 60% which is responsible for the quality of sound joint with no line interface.