Search

Post-weld heat treatment (PWHT) viz., annealing, normalizing and quenching was assessed regarding its effect on the microstructure and mechanical properties of pulsed Nd:YAG laser welded Hastelloy C-276/Monel 400 dissimilar sheets. The weld zone (WZ) microstructures of the different PWHT specimens exhibit finer dendrite grains along with Crrich carbides and Ni-rich oxide precipitates. The weld joints subjected to quenching attains near equal microhardness of the as-welded condition. During tensile testing, failures occurred in the WZ for quenched and normalized weld joints, whereas the Hastelloy C-276 fractured in annealed conditions, exhibiting ductile fracture mode. In corrosion studies the WZ of the weld joint subjected to annealing imparted superior corrosion resistance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The present study investigates the effect of laser shock peening (LSP) to enhance the metallurgical and mechanical properties of weld joints in Hastelloy C-276. The joint was fabricated by the gas tungsten arc welding (GTAW) with ERNiCrMo-3 filler wire. LSP was carried out on the top surface of the fusion zone. An optical microscope and a scanning electron microscope (SEM) were used to compare the as-welded and laser shock peened microstructure on the fusion zone. The results show that the refined microstructure was observed in the laser shock peened fusion zone compared with the as-welded microstructure. The X-ray diffraction (XRD) result shows a 50% reduction in grain size after LSP. The effect of microsegregation also reduced in the laser shock peened zone. The laser shock peened zone shows slightly higher surface roughness, and improved hardness and strength compared to as-welded zone. [ABSTRACT FROM AUTHOR]