Systematic Phase-Field Study on Microstructure Formation During Brazing of Mar-M247 with a Si-Based AMS4782 Filler

Abstract

Although advanced solidification processes like high temperature brazing have gained more and more industrial importance, they still are often not well understood, and defining optimal process conditions for practical use in many cases can be achieved only by expensive experimental trial and error methods. On the other hand, the phase-field method has become more and more powerful for the simulation of solidification and phase transformations in technical alloys. This paper presents phase-field simulations for high temperature brazing of the Ni-base superalloy Mar-M247 using a Si-based AMS4782 filler. The applied phase-field model can be online-coupled to Calphad databases which deliver the thermodynamic and mobility data for this complex multicomponent multiphase alloy. Unknown or uncertain physical parameters like diffusion coefficients have been calibrated by comparing to optical micrographs and EDX element mappings obtained from laboratory braze experiments for the same material combination. By variation of the process conditions the effects of the brazing temperature, the brazing time, and the thickness of the braze gap on precipitation of brittle phases and formation of stray grains as well as changes in the microstructure of the base material itself have been systematically investigated. Results are presented and discussed.

Appendix A: Model Parameters and Assumptions for Brazing Simulation

See Tables A1, A2, and A3.

Table A1 Phase-Related Parameters Assumed in Brazing Simulations

Table A2 Phase Interaction Parameters Assumed in Brazing Simulations

Table A3 Nucleation Parameters Assumed in Brazing Simulations