Microstructure evolution of laser repair welded René 77 nickel-based superalloy cast

Abstract

This study performed repair-welding tests on René 77 Nickel-based superalloy by adopting a Nd:YAG pulsed laser technique, coupled with René 41 filler wire and various welding parameters. After welding, the microstructure evolution, crack behavior and mechanical properties of the welds were determined by a combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and micro-hardness test. The experimental results showed that, due to suffering from different thermal histories during the conduction of the multi-pass welding process, the microstructures within the welds had split into six zones. In terms of cracking behavior, no cracks formed in the weld fusion zone (WFZ) or the heat-affected zone (HAZ) under appropriate welding parameters; however, setting the laser energy too high resulted in weld centerline cracking or intergranular cracking in the weld fusion zone. Moreover, various types of liquation cracks may occur at the interface between the WFZ and the HAZ. © 2011 The Japan Institute of Metals.