Studies on the effect of filler wires on micro level segregation of alloying elements in the alloy 617 weld fusion zone

Abstract

Highly corrosion resistance nickel based superalloy 617 (UNS N06617) usually opts for high-temperature applications. This alloy is a constituent of alloying elements such as Cr, Co, and Mo, it also acts as solid solution strengtheners. The elements Mo and Cr segregation are prone to cracking tendency in this alloy. The current work investigates the mechanical and metallurgical behavior of the weldments produced by four different filler metals. The weldments were made by using Continuous current Gas Tungsten Arc Welding (CGTAW) technique with ERNiCrCoMo-1, ERNiCrMo-10, ERNiCrMo-4, and ERNiCrMo-14 filler metals. The existence of columnar and cellular structures in the weld zone was observed through microstructural inspection. Scanning Electron Microscope (SEM) confirmed the secondary phase existence in the subgrain boundaries region (SGBR) of all the weldments. Through Electron Dispersive Spectroscopy (EDS) examination Cr-rich phases were observed in ERNiCrCoMo-1 filler metal and Mo- rich phases in other filler metals (ERNiCrMo-10, ERNiCrMo-4, and ERNiCrMo-14). Weldment produced by ERNiCrCoMo-1 filler metal shows marginally higher tensile strength compared to the other weld joints. Ductile mode of failure was observed through SEM fractography for all the weldments. Results of bend test didn’t show any crack in the surface regions.