Microstructural characterization, mechanical properties and corrosion behaviour of pulsed current GTA welded bimetallic joints between superalloy C-276 and stabilized austenitic stainless steel grade 321

Abstract

The present investigation articulates the effect of two varying welding heat inputs on the bimetallic weldments of superalloy C-276/stabilized grade 321 using pulsed current gas tungsten arc welding process. Experimental studies to understand the metallurgical as well as mechanical properties were carried out. The microstructures obtained in the high heat input weld consisted of columnar and cellular dendritic structure. On the other hand, the low heat input weld showed the occurrence of equiaxed and cellular dendritic structure. Moreover, the precipitation of Mo-rich intermetallic compounds was noticed in the fusion zone and at the interface of superalloy C-276. The absence of such precipitation in the low heat input weld resulted in an improved strength of the bimetallic weldments. Furthermore, the Polarization test was also conducted, which caused the higher heat input weld to corrode first at the regions around the intermetallic compounds and hence reduced Epit value was obtained.