Abstract
The iso-thermal oxidation of the quaternary Co-20Re-25Cr-3Si alloy at 1,000–1,200 C under laboratory air for 24 h has been studied. The oxidation kinetics at 1,000–1,200 C follow parabolic law perfectly and the value of oxidation activation energy is 220.74 kJ/mol. Unlike the experimental condition of 0.1 MPa pure oxygen, under laboratory air Co-20Re-25Cr-3Si alloy presents a good oxidation resistance due to the formation of a dense and continuous layer of Cr2O3 in contact with the alloy. A 79% drop in oxygen pressure has changed the oxidation mode from catastrophic oxidation to mild oxidation. The thickness of the protective Cr2O3 layer decreases when temperature increases. Therefore, Co-20Re-25Cr-3Si alloy shows the best oxidation resistance at 1,000 C. Moreover, from another perspective, compared with Co-17Re-23Cr-3Si alloy, the addition of about 2% Cr can also improve the oxidation resistance of the alloy greatly by forming the protective Cr2O3 layer.
Highlights
Superalloys are widely used in many fields such as aero engines, automobile engines, gas turbines, nuclear power, petrochemical industry, etc., and play an important role in economic development by virtue of its excellent oxidation and thermal corrosion resistance (Beran et al, 2016; Gorunov, 2017; Vorobiov et al, 2014; Shi and Zhong, 2010; Wanderka et al, 2016)
High temperature oxidation behavior of the quaternary Co-20Re-25Cr-3Si alloy under laboratory air has been studied in this paper
A 79% drop in oxygen pressure promotes the formation of a continuous dense protective Cr2O3 layer on the alloy, which prevents the evaporation of Re element in the alloy
Summary
Superalloys are widely used in many fields such as aero engines, automobile engines, gas turbines, nuclear power, petrochemical industry, etc., and play an important role in economic development by virtue of its excellent oxidation and thermal corrosion resistance (Beran et al, 2016; Gorunov, 2017; Vorobiov et al, 2014; Shi and Zhong, 2010; Wanderka et al, 2016). People pay more attention to low energy consumption and environmental protection, and pursue higher energy efficiency and less CO2 emissions They hope to develop superalloys that can serve at higher temperatures (Mukherji et al, 2012; Gorr et al, 2014a; Gorr et al, 2014b). There are a few reports about the oxidation behavior of the quaternary Co-Re-Cr-Si alloys under the condition of laboratory air or 0.1 MPa pure O2 (Gorr et al, 2012; Wang et al, 2013; Xu et al, 2020). High temperature oxidation behavior of the quaternary Co-20Re-25Cr-3Si alloy under laboratory air has been studied in this paper. The alloy microstructure and the constitution of oxides formed oxides were characterized by X-ray diffraction (XRD, Shimadzu XRD-6100) and scanning electron microscopy (FE-SEM, Zeiss Sigma) combined with energy-dispersive X-ray spectroscopy (EDS, Oxford INCA)
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