Alloy design of welding filler metal for 9Cr/2.25Cr dissimilar welded joint and mechanical properties investigation

In the work, a 5%Cr weld metal for the 9Cr/2.25Cr dissimilar welded joint was designed. The creep rupture, tensile, and impact behaviors of the weld metal and welded joint were tested and compared with those of the dissimilar welded joint with the 2.25%Cr weld metal. The result showed that the alloy design of the 5%Cr weld metal had a significant effect on reducing the degree of carbon migration at the joint interface. The interfacial creep damage and early failure tendency were reduced greatly. V and Nb in combination with N were added to enable creep strength at elevated temperatures by the formation of MX particles. Creep rupture tests at 540 °C showed good agreement with the alloy design, and no failures were observed in the weld metal for long-term cross-weld creep specimens, indicating that the newly designed 5%Cr weld metal was of adequate creep strength for use with dissimilar welded joint. The excellent tensile strength and adequate toughness showed good agreement with the rationality of tempering parameters.