Development and analysis of Hastelloy-X alloy butt joint made by laser beam welding

Abstract

The investigation describes the processing and analysis of laser welded Hastelloy-X (HX) alloy joints through this paper. HX alloys are employed in aerospace and nuclear industries, especially for high-temperature applications. In this research, a series of laser beam welding (LBW) experiments denoted as E1 to E9 were conducted on the HX base metal (BM), adhering to the L9-orthogonal array (L9-OA) design matrix. CO₂ laser technology was employed to fabricate HX butt joints. The laser power, focal length and welding speed were the variables. Then, the character of each joint was analyzed by sophisticated testing methods as per ASTM standards. The results showed that the character of each sample was varied depending on the selection of parameters. The E5 sample had a maximum tensile strength (TS) and ductility with 93 % joint efficiency. The grain elongation and refinement in the weld zone (WZ) were confirmed through microstructures and electron back scattered diffraction (EBSD) studies. The corrosion character of each joint (E1 to E9) was analyzed using the potentiostatic polarization method. The E1 sample had the highest corrosion resistance. The corrosion rate was in the range of 7.4E−03 to 8.6E−05 mm/yr. The dry sliding wear test (A1 to A9) was carried out as per L9-OA on the E1 sample, since this weld parameter had good corrosion resistance, by varying applied load, sliding distances and sliding velocities. Wear test results showed an increase in wear rate with the increase in load and sliding distance. A wear map was also drawn using the results to find out the association between wear rates and wear parameters. Weld speed had influenced the strength of the joint and laser power had shown an impact on the corrosion and wear of the HX alloy joints. The weld zone, corroded sample and the worn-out surfaces of weld joints were further analyzed using an optical microscope (OM) and Field Emission Scanning Electron Microscopy (FESEM).