Effect of pulse energy on microstructure and properties of laser lap-welding Hastelloy C-276 and 304 stainless steel dissimilar metals

Abstract

Nd:YAG pulsed laser lap-welding of Hastelloy C-276 and 304 stainless steel was conducted. The effect of pulse energy on weld morphology, element distribution, microstructure, phase structure, tensile-shear property and corrosion property of weld joint was analyzed. The results indicated that, with the increase of pulse energy, both the penetration depth and bead width of weld metal (WM) and dilution level of 304 base metal (BM) were linearly increased. Unmixed zone between WM and 304 BM was reduced, however, the grains sizes in WM became coarser. The precipitated phase with higher content of Mo and W is mainly p phase, with the increase of pulse energy, segregation potential of Mo element was increased, however, the amount of precipitated phase was decreased due to a decline in Mo element in WM. The fracture mode of weld joint transferred from interfacial fracture to tensile fracture with the increase of bead width, and the maximum load capacity of which was achieved at a pulse energy of 4.0 J. The average micro-hardness value of WM was decreased with the increase of pulse energy due to the depletion of Mo and W strengthening elements and the coarser grain size in WM. The corrosion resistance of WM was weakened with the increase of pulse energy ascribed to the reduce of Ni and Mo elements.