Published online by Cambridge University Press: 30 January 2017
The challenges of a high temperature environment impose severe material performance constraints in terms of melting point, oxidation resistance and structural functionality. In metallic systems the multiphase microstructures that can be developed in the Mo-Si-B system and Nb silicide alloys offer useful options for high temperature applications. Since the alloy compositions that exhibit the lowest oxidation rate will most likely not yield optimum mechanical properties performance, it is important to develop robust and compatible oxidation resistant coatings. An effective strategy to achieve the necessary environmental resistance is based upon the use of an integrated Mo-Si-B based coating that is applied by a pack cementation process to develop an aluminoborosilica surface and in-situ diffusion barriers with self-healing characteristics for enhanced oxidation resistance. The environmental performance requires resistance not only to high temperature oxidation, but also resistance to water vapor, CMAS (calcia-magnesia-aluminosilica) attack, hot corrosion and thermal cycling. Under these extended environmental conditions the Mo-Si-B based coating exhibits robust performance.