The liquation cracking behavior of IN738LC superalloy during low power Nd:YAG pulsed laser welding

The liquation cracking behavior of low power pulsed Nd:YAG laser welded IN738LC was studied using several pre-weld heat treatment cycles. The results showed that liquation cracks in the alloy were associated with grain boundaries constituents such as gamma-gamma' eutectic, MC carbide, Cr-Mo boride and Ni-Zr intermetallic. The liquation cracking in the weld heat affected zone (HAZ) was observed to be affected by the hardness of base-alloy. In addition, the results revealed that the presence of Cr-Mo rich borides in the pre-weld alloy constitutes a major factor enhancing susceptibility to Equation cracking. The boride particles reduce the temperature at which non-equilibrium intergranular liquation initiates in the HAZ, during the heating cycle of welding. Gleeble physical simulation revealed that in samples heat treated at 1050 degrees C for 2 h, the Equation started at significantly lower temperatures than in 1120 degrees C solution heat treated samples, this is attributed to the occurrence of the boride particles in the 1050 degrees C samples, which had dissolved by the 1120 degrees C heat treatment. (C) 2012 Elsevier Inc. All rights reserved.