Effect of Nd:YAG pulsed-laser welding parameters on microstructure and mechanical properties of GTD-111 superalloy joint

Abstract

GTD-111 nickel-based superalloy possesses high-temperature strength and suitable creep properties due to the presence of a high volume fraction of γ′ phase; and, it is widely used in aerospace industries including manufacturing of gas turbine blades. In this study, autogenous welding in conduction mode was performed using pulsed Nd:YAG laser on GTD-111 sheet with a thickness of 1 mm. By changing pulse frequency, pulse duration, and welding speed parameters, the consequent changes in the welding properties were investigated. The results of microstructural studies using optical and electrical microscopy revealed that when the pulse frequency and pulse duration increase, the susceptibility to liquation and solidification cracks decreases, The most important reason of which is the decrease in the cooling rate of the welding due to the increase in the heat input. Despite most of the performed researches, in this study, by increasing the welding speed, the susceptibility to liquation and solidification cracks decreases, The most important reason of which is the omission of plasma effect on the weld pool. It was defined that by pulsed Nd:YAG laser with a pulse frequency of 20 Hz, a pulse duration of 7 mm, and a welding speed of 8.3 mm s−1, a welding with full diffusion without any cracks can be obtained; the results of tensile and hardness tests also approve this matter.