High-performance brazing of single crystal superalloys with Ni-Cr-Ta filler material

High -performance joining especially brazing has been highly expected in the manufacture or maintenance of single crystal blades. In this paper, a Ni-40Cr-10Ta (at.%) alloy was developed as filler material for single crystal superalloys. High -performance brazing of DD5 superalloy was achieved. The joints brazed at 1260 degree celsius contained an isothermal solidification zone (ISZ) with "gamma + gamma '" structure and an athermal solidification zone (ASZ) composed of gamma, gamma', gamma/gamma '-eutectics, TaCr2 and TaC. Unlike the conventional filler materials with melting point depressants of B and Si, the Ni -Cr -Ta filler material was free of B and Si, and thus the resulting joints contained no B-rich and Si-rich compounds and eutectics with low melting points, which enhanced the brazed joint performance. The tensile strength at 980 celcius of the heat-treated joints reached 654 MPa, which is 88.5 % that of the base metal.