Oxidation of a Mo-Si-B-Ti Alloy

The oxidation of a titanium (Ti)-modified Mo-Si-B alloy designed for aerospace applications was investigated. Test samples were produced using arc melting and laser powder bed fusion (LPBF) additive manufacturing methods. To address high-temperature oxidation, a three-step coating strategy was employed, comprising a Mo precoat, Si and B co-deposition, and a conditioning step for the formation of a self-healing coating. The study evaluates the oxidation resistance of both uncoated and coated Mo-Si-B-Ti alloys at temperatures ranging from 1100 to 1300 °C. Uncoated alloys exhibited catastrophic mass loss within 10 hours at temperatures between 800 and 1300 °C. In contrast, the coated samples demonstrated minimal mass loss at 1300 °C after 50 hours, with only minor mass gain observed under cyclic thermal loading after 300 cycles. Microstructural analysis revealed distinct differences between arc-melted and LPBF samples, with the latter displaying an ultrafine dendritic microstructure. The applied coating effectively prevented oxygen diffusion into the substrate, even at elevated temperatures, showcasing its protective capabilities. During cyclic tests, the coating exhibited a self-healing mechanism, with cracks filled with borosilica contributing to prolonged environmental resistance.