ELEVATED TEMPERATURE COATING LAYER DESIGNS FOR Mo-Si-B ALLOYS

摘要

Several multiphase coating strategies have been examined for enhancing the high-temperature oxidation resistance of Mo-Si-B alloys. The central theme of the coating design is to impart an effective deterrent to oxygen penetration through the coating by means of controlling the critical factor of Boron to Silicon compositional ratio in the surface layer. The deposition of an external coating such as a silica layer has been shown to alter the chemical composition of the naturally occurring borosilicate oxide, resulting in a significant improvement in the oxidation resistance. Similarly, the development of an in-situ coating of silicide phases (MoSi_2 and/or Mo_5Si_3-B) as well as gradient layers has been demonstrated to be promising not only for a high-temperature oxidation barrier, but also as the foundation for a thermal barrier coating design.