Suppressing CMAS attack with a MoSiB-based coating

Molten CMAS (calcia–magnesia–aluminosilica) deposits penetrate and interact with thermal barrier coatings (TBCs) in gas-turbine engines to degrade the zirconia-based TBCs and the overall TBC performance. To address the CMAS attack some approaches have been advanced based upon sealing the TBC or altering the TBC composition. A new strategy is presented based upon the application of a MoSiB based coating applied by pack cementation. The interaction between the MoSiB-based coating on a Mo substrate and CMAS is evaluated on two types of natural CMAS sands and on a commonly studied synthetic CMAS. The MoSiB-based coating arrests CMAS melt penetration by an in-situ reaction that yields crystallization products that act to immobilize the CMAS. The coating design is demonstrated to be effective in preventing CMAS attack during isothermal exposure at temperatures up to at least 1500 °C and during thermal cycling.