Growth of an Mo2C Layer on Mo Surface During Carburization

This example uses the thermodynamic TCS Mo-based Alloys Database (TCMO) and its compatible TCS Mo-based Alloys Mobility Database (MOBMO) with the Add-on Diffusion Module (DICTRA) to study layer growth on a surface during carburization.

Read more about the Diffusion Module (DICTRA) on our website. There is also a Getting Started with the Diffusion Module (DICTRA) page available. If you are in Thermo‑Calc, press F1 to search the help to learn about the available settings included with the Add-on Module.

The inward diffusion of carbon into Mo-based alloys during carburization can lead to the formation of Mo carbides due to the low solubility of carbon in the metal matrix. Within the Mo2C layer, carbon diffusivity is significantly higher than that of molybdenum, resulting in the primary inward growth of the Mo2C layer. Consequently, this growth process can be considered as occurring in a closed system.

The following example shows the results from the Diffusion Module (DICTRA) simulation of pure Mo metal exposed to a carbon dioxide-containing gas atmosphere by using the most recent versions of the Mo-based databases (TCMO2 and MOBMO2).

The growth of Mo2C layer is simulated with a boundary condition of acrC=1 using the moving boundary model, with a temperature range of 1273-1673 K for 64 h.

The simulated growth of Mo2C layer on the Mo surface with a boundary condition and at 1273-1373 K for 64 h

Figure 1: The simulated growth of Mo2C layer on the Mo surface with a boundary condition of acr(C)=1 using the moving boundary model, with a temperature range of 1273-1373 K for 64 h, compared with the experimental data from [1983Ros].

The simulated growth of Mo2C layer on the Mo surface with a boundary condition and temperature range of 1473-1673 K for 64 h,

Figure 2: The simulated growth of Mo2C layer on the Mo surface with a boundary condition of acr(C)=1 using the moving boundary model, with a temperature range of 1473-1673 K for 64 h, compared with the experimental data from [1983Ros].

Reference

[1983Ros] C. J. Rosa, Carbon diffusion in Mo2C as determined from carburization of Mo. Metall. Trans. A. 14, 199–202 (1983).