Effect of heat input on microstructure and mechanical properties of laser welded dissimilar grade nickel alloys

Abstract

This study reports the effect of heat input (21.3–41.3 J/mm) on the microstructure and mechanical properties of pulsed Nd: YAG laser butt welded UNS N10276 (Hastelloy C-276) and UNS N4400 (Monel 400) sheets. The different heat input was achieved by changing the experimental parameters viz., welding speed (350, 400, 450 mm/min), pulse energy (8, 10, 12 J) and pulse width (5, 6, 7 ms). Though the weld macrostructure exhibit full penetration, the morphology and top weld width differs for the attempted conditions. Weld zone microstructures at lower, medium and higher heat input conditions display unmixed islands, dendrite grains with a slender heat affected zones (HAZ) and Cr-carbide rich reaction compounds respectively. Highest micro-hardness is witnessed for a heat input of 30 J/mm. The tensile strength of the weld joints reaches a maximum and tends to decrease with the increasing heat input.