Effect of filler metal on the microstructural evolution and mechanical properties of wide gap brazed K417G superalloy joints

Ni-based superalloy K417G was brazed using different contents of additive alloy + braze alloy mixed powder filler metal. The effect of filler metal constitutions on the microstructural evolution and mechanical properties of the joint was examined in detail. The interfacial formation mechanisms of K417G alloy brazed joint were analyzed. Results indicated that the gamma + gamma' matrix phase first forms at the wide gap brazing region during brazing . B segregation appeared and borides formed fine particles of M3B2. The M3B2 phase and gamma/gamma' eutectic phase were derived from the residual liquid phase during the cooling process. The boride size and formation of gamma/gamma' eutectic phase with a low melting point were restrained when the proportion of additive alloyincreased; thus, the microstructural homogeneity of the wide-gap brazed region was improved. B atoms uniformly diffused through the K417G alloy and its additive alloy when the proportion of additive alloy was increased to 95 wt.%. The tensile properties of the joint were improved due to the absence of a low-melting-point eutectic phase and a significant reduction in the number of brittle borides.