A mathematical model describing carburization in multielement alloy systems

Abstract

Previously, a finite difference model was set up describing the diffusion of carbon in high-temperature model alloys and its chemical reaction with one of the alloy components. The model described the formation of up to three different chromium carbides, two of which could coexist. This paper describes the further development of the model for application to commercial alloys. The model was extended to enable treatment of an arbitrary number of (a) metallic carbide-forming components in the alloys, (b) carbides which may form, (c) components out of which each carbide may be composed, and (d) carbides which may coexist. With this model, carbon concentration profiles and distribution profiles of precipitated carbides occurring during carburization of binary, ternary, and quaternary Ni-based alloys were calculated. Kinetic and thermodynamic data needed for the calculations were obtained by combining literacture data with experimental results and by fitting measured with calculated concentration profiles. The resulting calculated carbon profiles and carbide distributions were in good agreement with the experimental results.