Study on the mechanism of Ni-26W-6Cr alloy solidification cracking: Effect of laser welding heat input

Abstract

The segregation of P, S, Al, Si and Mo at solidification grain boundary (SGB) results in the formation of the low-melting-point liquid film. As heat input (HI) increases from 76.9 to 214.3 J/mm, upper weld seam width increases by 63 % and lower seam width decreases by 29.3 %. High welding HI generates lower temperature gradient, which could reduce thermal stress. The average hardness of weld metal (WM) drops from 273 to 235 HV and there is a 90 % reduction in the total length of welding solidification crack (WSC). The lower hardness under high HI facilitates the release of thermal stress, which permits the WM to accommodate the tensile stress generated during the solidification phase. Reduced thermal stress decreases the driving force of the formation of WSC.