Tungsten inert gas welding of zircaloy sheet: Mechanical properties and microstructural characterization Wolframinertgasschweißen von Zirkoniumlegierungsblechen: Mechanische Eigenschaften und mikrostrukturelle Charakterisierung

Abstract

A zirconium-based alloy called zircaloy-2 is well known for its exceptional resistance to corrosion and low cross-sectional absorption of neutrons, which makes it a vital component for fuel cladding application in the nuclear industry. Tungsten inert gas welding is an effective method for joining zircaloy due to its precise heat control and inert gas shielding, ensuring high-quality welds with minimal contamination. This technique is particularly advantageous for applications demanding excellent corrosion resistance and mechanical properties. Fabrication of zircaloy-2 sheets through tungsten inert gas welding, guided by optimal process parameters derived from extensive trial-and-error testing, has yielded welds with impeccable quality suitable for deployment in nuclear, aerospace, and marine sectors. Analysis of welded microstructure of material revealed the presence of columnar and equiaxed dendrites near the weld metal, primarily composed of α-zirconium and β-zirconium phases, as evidenced by optical microscopy and x-ray diffraction. These microstructural variations, induced by constitutional supercooling and thermal histories, have significantly enhanced the mechanical properties of welded pipe. There is an increase of 4.3 % in strength as tensile strength of 477 MPa, while base metal exhibited strength of 457 MPa. Notably, the welded sheet exhibited superior mechanical strength compared to the base metal, with ductility demonstrated through a 180° bend test showing no signs of cracking proving its ductility. Microhardness assessments highlighted a decline in hardness within the base metal region (178 HV 0.5 to 186 HV 0.5), contrasting with peak values observed in the weld metal (215 HV 0.5 to 223 HV 0.5). This comprehensive investigation sheds light on the successful fabrication of zircaloy-2 via tungsten inert gas welding, emphasizing its potential for diverse industrial application.