Study of melting efficiency, micro-segregation, and corrosion resistance of Ytterbium fiber laser welded Hastelloy C-276 sheet in pulsed wave mode

Abstract

ABSTRACTWelding of Hastelloys using higher value of ‘linear heat input' decreases corrosion resistance due to the increase in micro-segregation of elements in the weld zone. 'Melting efficiency' of heat source could be an important parameter to control the heat input and micro-segregation of elements in the weld zone. In the present study, bead-on-plate welding was carried out on 3-mm-thick Hastelloy C-276 sheet at constant laser power and varying scan speed in pulsed mode, and the melting efficiency was found to be 30%. A study of ‘segregation ratio’ of elements in the weld zone showed that the amount of micro-segregation of molybdenum was found to increase with the increase in linear heat input. Increase in the segregation of molybdenum could cause a decrease in corrosion resistance of the welded specimen. Hence, a confirmation test (i.e., corrosion test) was performed to study the effect of linear heat input on the corrosion resistance of the welded sample due to micro-segregation. It was observed that the increase in linear heat input causes an increase in micro-segregation as well as an increase in corrosion rate. X-ray diffraction analysis showed that the concentration of passivating phases was found to increase with the increase in scan speed.