Growth of an Mo₅Si₃ Layer in Mo/MoSi₂ Coatings at High Temperatures

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 in coatings at high temperatures.

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.

To enhance the high-temperature oxidation resistance of Mo-based alloys, applying a MoSi₂ ceramic coating on the substrates is highly effective because it forms protective SiO₂ scales on the coating's surface. Moreover, since Si atoms diffuse into Mo substrates more rapidly than Mo atoms, this inward diffusion of Si results in the formation and growth of a Mo₅Si₃ layer.

The following example shows the results from the Diffusion Module (DICTRA) simulation of Mo substrate joined with an MoSi₂ coating material by using the most recent versions of the Mo-based databases (TCMO2 and MOBMO2). The growth of the Mo₅Si₃ layer between the Mo substrate and MoSi₂ coating is simulated using the homogenization model, with annealing temperatures ranging from 1473 K to 1773 K for 30 s.

The thickness of Mo₅Si₃ was estimated based on the Mo concentration profiles in the Mo/MoSi₂/Mo₅Si₃ diffusion couple at different times and temperatures. In this case, TC‑Python was used to generate the plot shown in Figure 1.

Read more about TC-Python and its capabilities on our website. Scroll to the bottom of the page to access several resources such as videos, publications, blogs, documentation, and much more.

Reference

[2022Yan] J. Yan, Y. Z. Lin, Y. Wang, J. Qiu, F. Wan, C. Song, Refractory WMoNbVTa high-entropy alloy as a diffusion barrier between a molybdenum substrate and MoSi2 ceramic coating. Ceram. Int. 48, 11410–11418 (2022).