OXIDATION PROTECTION OF Mo-Si-B ALLOYS BY MAGNETRON-SPUTTERED COATINGS

摘要

Mo-Si-B alloys with melting temperature above 2000°C are attractive high temperature materials offering significantly enhanced operating temperatures compared to those of the currently used Ni-based superalloys. However, their oxidation behavior is poor at temperatures below 1000°C, suffering from evaporation of MoO_3. Above 1000°C oxidation is characterized by a transient state showing considerable mass loss followed by a steady state condition with reduced mass change. To mitigate this degradation by oxidation, application of coatings is an appropriate method ensuring the formation of slowly growing protective scales.