Multi-objective optimization and fracture analysis of laser weld joints of Ni-Cr superalloy 80 A for gas turbine components

This article addresses butt joining of 1.2 mm thick Ni-Cr superalloy 80 A sheets using a 3.5 kW CO₂ laser beam welding (LBW) process, which is critical for gas turbine components, nuclear tube supports and automotive valves in high temperature applications. LBW, chosen for its low heat input and minimal heat-affected zones, was optimized using Taguchi-based gray relationship analysis. The L9 orthogonal array experiment identified the optimal parameter sets for welding speed, laser power, focal length, and shielding gas flow rate that affect tensile strength, microhardness, penetration depth and weld bead. The results were validated using ANOVA analysis, fractography, hardness testing, micrographs and tensile tests. Microstructural variations in fusion and heat affected zones. The optimized parameters resulted in a tensile strength of 817 MPa and a microhardness of 292 HV, demonstrating improved weld quality.