Water cooling assisted laser dissimilar welding with filler wire of nickel-based alloy/austenitic stainless steel

Abstract

To clarify the effects of water cooling on solidification behavior of pulsed laser welding of Nickel-based alloy/austenitic stainless steel with filler wire, and to improve the mechanical properties of laser welded joints, the analyses of morphology, microstructure, anti-peel property and micro-hardness were carried out. The results indicated that adding water cooling increased cooling rate and temperature gradient of the weld. And the addition of water cooling made constitutional supercooling of the weld easier, so that the solidification rate increased with the increase of the temperature gradient. Therefore, the weld grain was refined by about 28%, and the average width of unmixed zone decreased by 35%, with a low volume fraction of Mo-rich precipitated phase consisting of p phase and μ phase. The μ phase was discovered in laser welding Nickel-based alloy/austenitic stainless. Both p phase and μ phase had a good coherent relationship with the matrix, which resulted in the low phase boundary energy between precipitated phase and matrix. The coherent relationship is described as [1 4 3] p // [5 3 1] γ between the p phase and the matrix. And the coherent relationship is described as [1 2 0] μ // [2 2 1] γ between the μ phase and the matrix. There are the stacking faults in the μ phase along the direction of [1 1 0], which is one of the slip system in μ phase. At the same time coherent relationship between p phase and matrix is better than that of μ phase. The micro-hardness, load capacity per length, and anti-peel stress were improved by 10.5%, 8.1%, and 11.8%, respectively.