Effect of carbon migration on mechanical properties of dissimilar weld joint

After welding or servicing at high temperature, carbon migration will occur in dissimilar welded joint. Correspondingly, the carburized layer with high carbon content and decarburized layer with low carbon content are formed near weld fusion line. Carbon migration has a great influence on the properties of the joint and leads to premature failure. However, due to the small size of carburized layer and decarburized layer, it is difficult to use the traditional uniaxial tensile test method to study their mechanical properties. In this work, the elastoplastic properties of base metal (BM), carburized zone (CZ), decarburized zone (DZ) and weld metal (WM) in A302/ Cr5Mo dissimilar weld joint were investigated by nanoindentation tests. nanoindentation tests results indicate that the decarburized zone is the weakest position in the weld joint. Metallographic and carbon content distribution analysis were also carried out and found that the width of CZ is related to the width of fusion zone (FZ) and the CZ does not exceed the boundary of FZ.