Microstructure and Strength Evolution in Laser Welded Hastelloy C-276 Nickel-Based Alloy Sheets Under Different Thermal Energy Conditions
S. Saravanan
Hastelloy C-276 (UNS N10276) nickel-based alloy is widely employed in the fabrication of nuclear reactor components and corrosive resistant equipment. In this work Hastelloy C-276 sheets were butt welded by a pulsed Nd:YAG laser welding machine at different thermal energy conditions. The resulting variation in macrostructure, microstructure and mechanical properties are presented. The thermal energy supplied (beam power/weld speed) was altered by varying the operational parameters viz. weld speed (350 to 450 mm/min), laser beam energy (10 to 14 J) and laser beam pulse width (6 to 8 ms). The weld macrostructures were seen to be free from cracks and defects, exhibiting complete penetration and the crest (top width) of the weld increases with the thermal energy supplied. In the microanalysis, growth of dendrite grains from periphery to mid-section of the weld was observed. In addition, Mo rich compounds and carbides are witnessed in the weld zone (WZ) for higher thermal energy conditions. The tensile and yield strengths of the weld joints are inversely proportional to the thermal energy supplied.
Keywords: Nd:YAG laser, nickel-based alloy, Hastelloy C-276, UNS N10276, laser welding, microstructure, tensile strength, yield strength, thermal energy