Hot corrosion behavior of Mo-Si-Ti alloys

The hot corrosion behavior of two ternary Mo-Si-Ti alloys (eutectic Mo-20.0Si-52.8Ti (at.%) and eutectoid Mo-21.0Si-34.0Ti (at.%)) was investigated at 700 degrees $700<^>\circ $C and 900 degrees $900<^>\circ $C for up to 100 h. Both Mo-based alloys evidenced a hot corrosion attack, resulting in a uniform attack of the substrate surface. The higher Ti content of the eutectic alloy significantly reduced the formation of solid and volatile Mo oxides compared with the eutectoid alloy. After 24 h at 700 degrees $700<^>\circ $C, the corrosion products formed on the eutectic alloy were only one-tenth the thickness of the layers formed on the eutectoid alloy. The corrosion products were examined with optical and electron microscopy. Semiquantitative electron probe micro analysis and X-ray diffraction measurements were used to identify the formed phases. The underlying corrosion mechanisms comprising not only hot corrosion-induced fluxing but also oxidation-induced pesting are discussed in detail. Both Mo-Si-Ti alloys were subject to hot corrosion attack at 700 degrees $700<^>\circ $C and 900 degrees $900<^>\circ $C, resulting in a uniform attack of the substrate surface. The mechanisms differed from the classical hot corrosion, and the severity of the attack and the corrosion products formed are highly dependent on the alloy composition. image