Abstract Scope |
The development of alternative high-temperature materials with advanced high-temperature capability compared to commercially applied Ni-based superalloys is challenged by achieving resistance to both, chemical and mechanical degradation. The first is typically not fulfilled in Mo-Si-based alloys, which suffer from catastrophic oxidation, called ‘pesting’, due to volatilisation of MoO3 at temperatures below 1000 °C. However, novel Mo-Si-Ti alloys were found to exhibit pesting resistance under certain microstructural and chemical conditions. Their oxidation resistance is determined by the interaction of the high Ti-containing Mo solid solution and M5Si3 silicides, which is closely inter-related to a minimum nominal Ti content. Thus, the resistance to loading under creep conditions is pre-defined by the Ti to Mo ratio, which determines the solidus temperature of the alloys. The potential in creep performance is assessed at 1200 °C by (i) maximising the Mo content, (ii) adjusting the microstructural length-scale and (iii) considering strengthening phases like (Mo,Ti)5Si3. |