Microstructure and mechanical properties of DZ40M alloy brazed joint

Vacuum brazing of directionally solidified superalloy DZ40M was carried out using Co-Cr-Ni filler metal under different brazing parameters. The corresponding microstructure of the joint was investigated by means of SEM, WDS/EDS and XRD, and the high temperature creep rupture life and tensile strength was measured. The results show that the typical joint was mainly composed of base metal near the brazed seam, diffusion-reaction zone and the central zone. There were a few compounds in the base metal near the brazed seam. The diffusion-reaction zone was made up with Co-base solid solution, carbides and borides. The central zone consisted of Co-base solid solution, gray borides and a small quantity of dark strips of carbides. The joint brazed at 1 180℃ for 30 min had the longest average creep rupture life tested at 980℃/83 MPa, which was 18 h 10 min. The tensile strength of all brazed joints tested at 900℃ were all higher than 305 MPa which is the technical standard value of base metal.