Computer aided alloy design of insert metal for transient liquid phase bonding of γ/γ'/β type high aluminium nickel base superalloy

Abstract

A computer aided alloy design technique was used to develop an insert metal for transient liquid phase bonding of γ/γ'/β type high Al, Ni base superalloy. A mathematical programming method was used to obtain an optimal chemical composition through rationally compromising the plural objective performances of an insert metal using the grid search method. This approach was based on data estimation from limited experimental data using the interpolation method. The objective function Z, which was introduced as an index of bonding performance of an insert metal, involved the melting point, hardness, formability of brittle phases, and void ratio in the bond layer as the evaluating factors. Using this method, the chemical composition Ni-3.0Cr -4.0B-0.5Ce (mass%), designated HY- 20, was determined as the optimal composition for the insert metal. Observations using SEM revealed that the joints bonded with the newly developed insert metal exhibited sound microstructures without the formation of brittle phases and voids in the bond layer. The creep rupture properties of the joints bonded using the HY- 20 insert metal were much improved as compared with the commercial Ni base amorphous insert metal MBF -80 (Ni-15.5Cr-3.7B), and were fairly comparable to those of the base metal.