Abstract
In this study, the ultrahigh-temperature tensile creep behaviour of a TiC-reinforced Mo-Si-B-based alloy was investigated in the temperature range of 1400–1600 °C at constant true stress. The tests were performed in a stress range of 100–300 MPa for 400 h under vacuum, and creep rupture data were rationalized with Larson-Miller and Monkman-Grant plots. Interestingly, the MoSiBTiC alloy displayed excellent creep strength with relatively reasonable creep parameters in the ultrahigh-temperature range: a rupture time of ~400 h at 1400 °C under 137 MPa with a stress exponent (n) of 3 and an apparent activation energy of creep (Qapp) of 550 kJ/mol. The increasing rupture strains with decreasing stresses (up to 70%) and moderate strain-rate oscillations in the creep curves suggest that two mechanisms contribute to the creep: phase boundary sliding between the hard T2 and (Ti,Mo)C phases and the Moss phase, and dynamic recovery and recrystallization in Moss, observed with orientation imaging scanning electron microscopy. The results presented here represent the first full analysis of creep for the MoSiBTiC alloy in an ultrahigh-temperature range. They indicate that the high-temperature mechanical properties of this material under vacuum are promising.
Highlights
Many key technologies rely on systems that operate at elevated temperatures, ranging from energy conversion systems in automotive applications and power plants to propulsion systems in aircraft engines and rockets
Interest in the high melting point of melting points than Ni (Mo) arises from the fact that vacancy densities scale with the relative distance to the melting point and different homologous temperatures, Th, which expresses the temperature of a material as a fraction of its melting point (T/Tm; temperatures in K)
MoSiBTiC alloy mainly consists of three phases: a Mo-rich solid solution Moss (Mo base with 2.5 at% Ti and 1.9 at% Si, crystal structure: bcc), which appears as a white contrast; a Mo5SiB2-type intermetallic compound known as T2, which appears grey; and a (Ti,Mo)C-type carbide, which appears as a black contrast
Summary
Many key technologies rely on systems that operate at elevated temperatures, ranging from energy conversion systems in automotive applications and power plants to propulsion systems in aircraft engines and rockets. High-temperature processes and critical high-temperature components can differ in many ways; their common aspect is a steady driving force for increased thermal efficiencies, as expressed by the second law of thermodynamics[1,2] Researchers in this field aim to develop materials that can operate at higher service temperatures. Because single-phase alloys do not exhibit good high-temperature strength, they need to be strengthened with fine particle dispersoids Refractory metals such as Mo have much higher melting points than Ni (Mo: 2623 °C5); Mo-based alloys are considered attractive candidates for ultrahigh-temperature applications. Creep research in recent decades has shown that there is a need to strengthen metallic alloys with fine stable particle dispersoids[19,20,21,22,23,24], which has led to the development efforts discussed above[12,18]. This is represented by a combination of a power law and an Arrhenius-type equation as follows:
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
