Title

Enhanced oxidation resistance of high temperature Mo-Si-B alloys

Abstract

Mo-Si-B alloys are attractive due to their high temperature mechanical properties and high melting points. Oxidation develops initially with a transient stage due to the evaporation of the volatile MoO 3 and consequently to an initial high recession rate. Then a steady state stage begins when the developing borosilicate layer becomes continuous and protective. The transient stage is a key step in enhancing oxidation resistance of the Mo-Si-B alloys. The time for the formation of the continuous borosilicate layer depends on the fluidity of the glass, which varies with the boron to silicon ratio, the temperature and doping elements. Selected doping also limits the evaporation loss of MoO 3. In order to inhibit the transient stage and improve the oxidation performance, a kinetic bias concept which has been demonstrated to modify interface reactions is examined for coating applications. In order to achieve a compatible coating structure together with enhanced oxidation resistance, a pack cementation process is used to develop silicide, borosilicide and aluminide surface layers. The analysis of the enhanced oxidation performance clearly indicates that a kinetic bias strategy is effective for developing stable and robust coating systems.

Document Type

Conference Proceeding

Keywords

Coatings, Diffusion path, Doping, High temperature, Kinetics, Mo-Si-B alloys, Oxidation, Pack cementation

Publication Date

12-1-2008

Journal Title

17th International Corrosion Congress 2008: Corrosion Control in the Service of Society

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