Effects of TIG welding process on microstructure, electrical resistance and mechanical properties of Nichrome 8020

摘要

This study investigates effects of TIG welding and welding heat input on microstructure, hardness, tensile strength, fracture mechanism, and electrical resistance of Nichrome 8020 to evaluate its efficiency after welding, especially as a heating element. The post-weld microstructure of the alloy remained austenitic. The microstructure of fusion zone consisted of columnar dendrites, equiaxed dendrites, and intermetallic carbonitrides. These precipitates nucleated and grew among subgrain boundaries. Because of grain growth, hardness and tensile strength decreased after welding, and by increasing welding heat input, these mechanical properties decreased more severely. Fractography analysis showed that fracture surfaces of all the welded samples included both brittle and ductile features. Despite grain growth, which occurred as a result of the welding process, the electrical resistance of Nichrome 8020 increased slightly after welding. No signs of welding cracks and topologically close-packed phases were observed in the heat affected zone and fusion zone of any sample.