Interface Structure and Mechanical Property of F/A Dissimilar Metal Welded Joints

A special nickel-based weld transition joint has been designed for raising the creep strength and service life of the ferritic-austenitic dissimilar metal welded joints, which have been used in super-heaters of power plant boilers. The interface carbon diffusion, mechanical properties of joints and thermal stress on the interface area have been investigated by means of creep rupture tests, EDAX analysis, FE calculation. It is concluded that in the condition of elevant temperature and low stress, carbon migration and carbide precipitate in the fusion line and HAZ are important facters for effecting creep rupture and the nickel-based weld metal transiting joint can contribute to lower thermal stress and higher creep strength.