Microstructure and Its Influence on the Mechanical Properties of Ni-28W-6Cr-Based Alloy-Welded Joints by GTAW

Microstructure and mechanical properties of Ni-28W-6Cr alloy-welded joints produced by gas tungsten arc welding were investigated in this work. Results showed that original fine-grain base metal near fusion line totally transformed into coarse heat affected zone after welding. Carbides with different shapes were found in the weld metal and base metal, which all were determined as M6C carbides. In comparison with carbides in base metal, M6C carbides in weld metal are rich in Si and Cr but deficient in W. Moreover, M6C carbides are extremely scarce and hard to be detected in weld metal. Mechanical tests show that the hardness value of weld metal is only about 60% of base metal; the yield strength and tensile strength of welded joint are much lower than those of base metal due to the absence of carbides in weld metal.