Hot Corrosion of Mo–Si–B Coatings

The hot corrosion performance of the Mo–Si–B-based oxidation protection coating was evaluated. Mo coins coated by a Si–B pack cementation process were covered with a salt slurry and exposed to air at high temperature. This resulted in gradual mass losses attributed to spallation, as well as crystallization of the vitreous silica scale to cristobalite. Still air resulted in more severe attack than flowing air, owing to the stability of the salt scale that is established in stagnant air. Despite the hot corrosion attack, the coating retains the majority of the vulnerable Mo substrate after repeated thermal cycles for temperatures up to 1300 °C.