Microstructure and Mechanical Properties of Dissimilar Metal Weld Joint between VM12-SHC and X20 Martensitic Steels

In this paper, X20 and VM12-SHC martensitic steels were welded by tungsten inert gas (TIG) process. The microstructural and mechanical properties of the dissimilar weld joint were investigated. Results obtained indicated that the weld was comprised of typical tempered martensite microstructure. VM12 base metal (BM) had fine lath martensite while X20 consisted of large clusters of tempered martensite. Delta ferrite was distributed throughout the entire weld. The EDX results confirmed the presence of M23C6 and MC precipitates found on the grain boundaries and the matrix. Hardness test results revealed that the X20 CG-HAZ had exceeded the maximum hardness of 350HV-10, as per PN-EN 15614-1 and PN-EN 12952-6 standards for heat treated joints.