Hot corrosion behavior of two Mo-Si-Ti alloys at different temperatures

Due to their high melting point and creep strength, refractory elements such as Mo are promising candidates to be used in gas turbines. However, their utilization is usually restricted due to their insufficient oxidation and corrosion resistance. In this work, the hot corrosion resistance of two Mo-Si-Ti alloys, Mo-20Si-52.8Ti (at.%) and Mo-21Si-34Ti (at.%) is investigated in a SO2-containing atmosphere under Na2SO4 deposit at temperatures between 500 ◦C and 900 ◦C. After the hot corrosion tests, the samples are analyzed by XRD, SEM and EPMA. The objective of this study is to determine the temperature regimes, which promote degradation mechanisms of pesting and hot corrosion. Mo-21Si-34Ti (at.%) showed a pesting dominated behavior and a low corrosion resistance with rising temperature. Mo-20Si-52.8Ti (at.%) revealed a maximum corrosion rate at 600 ◦C, while it is reduced for higher temperatures because of the formation of a SiO2 layer at the surface.