Effect of Welding Parameters on the Liquation Cracking Behavior of High-Chromium Ni-Based Superalloy

Gas turbine blades working under extremely harsh operating conditions are made of superalloys. These superalloys are exposed to various damage mechanisms, which wear them out gradually. Welding is often preferred to repair the damaged components for cost minimization. This study aimed to investigate the effects of flexural load, heat input, and welding speed on the weldability and intergranular liquation cracking of high-chromium Ni-based superalloy. For this purpose, a series of Sigmajig tests designed based on the Taguchi method with L4 array, as well as microstructure investigations and residual stress measurements, were performed. The results showed that the microstructures of heat-affected zones (HAZs) were highly susceptible to cracking during the welding process, and all of these cracks appeared in the HAZ and grew perpendicular to the melting zone along grain boundaries. Flexural load contributed the most substantial impact (82%) on crack propagation compared with the 9.7 and 9.2% impacts of welding speed and welding heat input, respectively. We found that the lowest flexural load, welding speed, and heat input are the best welding parameters to reduce the total crack lengths at the welded area of high-chromium Ni-based superalloy.