Pulsed Laser Welding of Hastelloy C-276: High-Temperature Mechanical Properties and Microstructure

Based on the welding requirement during the coolant pump manufacture in the nuclear industry, the pulsed laser welding of 0.5mm thickness Hastelloy C-276 was investigated, and the well defect-free weld joint of less than 1mm width was obtained. According to the using temperature request of welding structure, the tensile test of as-welded samples at the high-temperature (200 degrees C, 300 degrees C, and 400 degrees C) and the scanning electron microscope (SEM) observation of fracture were conducted. It was found that some tensile samples were broken in the base metal and others were broken in the weld joint. The results indicated that the high-temperature yield strength, ultimate tensile strength and elongation of as-welded sample satisfied the demand compared to those of base metal. Also, the plastic deformation behavior of pulsed laser weld joint was not obviously changed, and just the plastic instability in the weld joint was restrained to some extent. In addition, the high-temperature fracture morphology in the weld joint indicated the weld joint fracture type belonged to the ductile fracture. At elevated temperature, the dislocation movement and reinforced element segregation resulted in the larger size of voids at the fracture, and the same voids characteristic between 200 degrees C and 400 degrees C indicated that the influence of the temperature on the dislocation movement and element segregation was not important.