Patrice Berthod
Abstract
In some high temperature applications, there is a constant need of refractory alloys able to resist oxidation by hot gases, hot corrosion by various melts and creep deformation. The best superalloys are currently the g/g’ nickel-based single crystals but they cannot be exposed to 1200°C and ...
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In some high temperature applications, there is a constant need of refractory alloys able to resist oxidation by hot gases, hot corrosion by various melts and creep deformation. The best superalloys are currently the g/g’ nickel-based single crystals but they cannot be exposed to 1200°C and more without losing their mechanical resistance. New principles of conventionally cast polycrystalline nickel alloys, combining good resistance against both hot gas oxidation and melts corrosion are explored in this work. Among them, the most promising system involves a reinforcement by HfC carbides. The studied alloy has kept its chromia-forming behaviour which allows good resistance against both oxidation resistance and corrosion by melts. Interesting for a nickel-based alloy containing no g’ precipitates, its creep resistance at 1200°C still remains to be improved to allow using it at so high temperature.
Abstract
High temperature tensile properties of 2D carbon-carbon composite made from high strength T700 carbon fibers were evaluated at different temperatures. Carbon-carbon composites were heat treated at different temperatures i.e., 750, 1000, 1500, 2000, 2500 °C and their tensile properties were measured ...
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High temperature tensile properties of 2D carbon-carbon composite made from high strength T700 carbon fibers were evaluated at different temperatures. Carbon-carbon composites were heat treated at different temperatures i.e., 750, 1000, 1500, 2000, 2500 °C and their tensile properties were measured at room temperature and at different high temperatures. It is observed that, maximum value of tensile strength at room temperature is of composite heat treated at 1500 °C thereafter strength decreases with increasing processing temperature up to 2500 °C. The decreases in strength are related to degradation of fiber properties in composites and in-situ damage. On the other hand, tensile strength is higher at high temperature compared to room temperature. It increases progressively with increasing the test temperature up to 2000 °C. Thereafter, strength decreases and ultimate value of tensile strength is less than that of the room temperature value of 2500 °C heat treated composites. Increase in strength up to 1500 °C is due to the improvement in fiber-matrix interactions, matrix properties due to relaxation of thermally induced stresses during high temperature test. Above 1500 °C enhancement in tensile strength is due to the enhancement in strength of carbon fibers and due to the creep deformation. Decrease in strength at measurement temperature 2500 °C is due to the additional in-situ degradation of fiber properties during high temperature test. Copyright © 2011 VBRI press.
