Investigation of the effect of filler metal type on the microstructure and mechanical properties of the joint in dissimilar welding of API ۵L X۵۲ / X۶۵ micro-alloy steels by GTAW method

In this study, the effect of filler metal on the microstructure and mechanical properties of dissimilar joint API X۵۲/X۶۵ was investigated. Welding was performed by tungsten-gas arc method with four filler metals ER-۸۰SNi۱, Inconel ۸۲ (ERNiCr-۳), Inconel ۶۲۵ (ERNiCrMo-۳) and ER۲۲۰۹. Microstructural observations showed that ER۸۰SNi۱ ferrite-austenitic weld metal, Inconel ۶۲۵ austenitic original phase with scattered precipitations in the grain boundaries, ER۲۲۰۹ has a two-phase structure consisting of ferrite and austenite layers and Inconel ۸۲ weld metal has a highly interstitial microstructural structure. The mechanical properties of the joints were investigated using microhardness and impact tests at ambient temperature. The presence of duplex and ferrite delta structures in the weld metal ER۲۲۰۹ increased its microhardness compared to other weld metals. Also, ERNiCr-۳ weld metal was less hard than other weld metals due to its austenitic and coarse structure. The results of impact test showed the highest and lowest fracture energies of ۲۳۳ and ۱۴۴ joules, respectively, for the weld metalobtained by welding with filler metals ER۸۰SNi۱ and ERNiCrMo-۳.

Keywords:

Micro alloy steel , X۶۵ , X۵۲ , filler metal , microstructure , microhardness , impact energy.