Mechanical properties of similar and dissimilar weldments of RAFMS and AISI 316L (N) SS prepared by electron beam welding process

Abstract

Effect of weld metal composition on microstructure and toughness of weld metal is studied in this paper. Weld joints of reduced activation ferritic/martensitic (RAFM) steel containing 1.0 and 1.4wt.%W were prepared using electron beam welding (EBW) process. Dissimilar weld joints between 1.0wt.%W RAFM steel and AISI 316L (N) SS were also prepared using EBW process. The effect of post weld heat treatment (PWHT) temperatures on microstructure and mechanical properties was also studied. Microstructural observation reveals delta–ferrite in 1.4wt.%W containing weld metal, which is absent in 1.0wt.%W weld metal. In the case of the dissimilar weld metal, microstructure shows presence of lath martensite and retained austenite. Austenite was stable even after PWHT and its presence is attributed to high nickel (5–6wt.%) content in the dissimilar weld metal. Hardness of RAFM steel weld metal was found to be 270–290 VHN after PWHT at 750°C for 2h. Impact toughness of both 1.0 and 1.4wt.%W RAFM steel is high (>250J) at ambient temperature. However, after PWHT, variation of toughness with temperature is more drastic for 1.4wt.%W RAFM steel weld metal than the other. As a result, ductile brittle transition temperature (DBTT) for the 1.4wt.% steel weld metal is close to 0°C while that of the 1.0wt.% W steel is close to that of the base metal (∼−80°C).