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

Abstract

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.

Influence of welding current on the microstructure, mechanical properties, residual stresses, and nano-mechanical behavior of tungsten inert gas-welded dissimilar joints of Inconel 625 and Incoloy 800

“…It can be observed that there is a decrease in hardness values in the fusion zone as compared to HAZ and base alloy 625. As it has been established that microhardness is inversely proportional to grain size 29,30 and the microstructural analysis, in the section Microstructural Analysis, it has been indicated that grain coarsening in the HAZ as of 625 side led to low hardness in 625 side HAZ for all the weldments. Specimen 1 showed relatively higher hardness (158 H v ) as compared to specimen 2 and specimen 3 with hardness values 126 H v and 157 H v , respectively, and this tendency can be attributed due to the presence of secondary phase precipitates, solid solution strengthening, and distinction in the dendritic structure.…”