Novel in situ synthesized carbide reinforced Ni base composite for structural castings with high creep resistance

Abstract

Ni base superalloys for structural castings of aero engines demand higher service temperatures and lower costs while retaining their processing characteristics. To achieve these properties, alloying with the rare precious metals inevitably leads to a decrease in the castability and a marked increase in the raw material cost. In this work, we develop a novel Ni base composite (MC/IN718C) with a high creep resistance, excellent microstructure stability and excellent castability by optimizing the chemistry and microstructure of the commercial IN718C superalloy. In this work, both tensile strengths at room temperature and at 704 °C were obviously improved, while the steady-state creep rate of the MC/IN718C composite at 704 °C was reduced by one order of magnitude. The rupture life of MC/IN718C at 704 °C/620 MPa was enhanced by one order of magnitude compared to the IN718C alloy due to the load bearing effect of the MC carbide, the elimination of the metastable strengthening precipitation phase γ″ and a decrease in the harmful Laves and δ phases. MC/IN718C Ni base composite presents a new strategy for the design and preparation of high-temperature materials potentially for critical structural castings. Keywords: Nickel superalloys, Carbides, Synchrotron radiation X-ray diffraction, Creep, Microstructure