Effect of Rhenium Addition on Hot Corrosion Resistance of Ni-Based Single Crystal Superalloys
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Effect of Rhenium Addition on Hot Corrosion Resistance of Ni-Based Single Crystal Superalloys J.X. CHANG, D. WANG, X.G. LIU, L.H. LOU, and J. ZHANG Hot corrosion behavior of two Ni-based single crystal superalloys containing 0 Re and 2 wt pct Re in molten sodium sulfate (Na2SO4) at 900 C in static air has been investigated using the ‘‘deposit recoat’’ method. It was shown that the incubation period of the Re-containing alloy was much longer than that of the Re-free alloy. It was because Re increased the stability of the chromium oxide (Cr2O3) scale, promoted the formation of nickel titanate (NiTiO3), and suppressed the diffusion of Ni. In addition, the overall corrosion kinetics of the Re-containing alloy followed a multistage parabolic law, compared with the Re-free alloy. This could be because Re increased the activity of chromium (Cr) and titanium (Ti), which resulted in the periodically opening and closure of the cracks in the outer oxide layer. https://doi.org/10.1007/s11661-018-4711-3 The Minerals, Metals & Materials Society and ASM International 2018
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INTRODUCTION
SINCE being identified in 1960s, hot corrosion has been given much attention and many achievements have been obtained.[1] Hot corrosion is initially caused by a sodium sulfate (Na2SO4) deposit resulting from the injection of salts into the engine and sulfur from the combustion fuel, so it remains an important property for large industrial gas turbines (IGTs) blade applications in those power plants located near to the seaside,[2] and where the fuel used for ITGs application is not of as high quality as for aero engines. Hot corrosion-resistant superalloys are extensively used in IGTs because of their outstanding mechanical strength and hot corrosion resistance. Due to the environment exacerbation and energy crises, more and more efficient power plants are required to reduce contamination and enhance thermal efficiency. One solution will be achieved by increasing the operating temperature of the turbines of the power plants.[3] Hence, the high-temperature strength of the hot corrosion-resistant superalloys must be further improved.
J.X. CHANG is with the College of Materials Science and Engineering, Xi’an Shiyou University, Xi’an 710065, China. D. WANG, X.G. LIU, and L.H. LOU are with the Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China. Contact e-mail: [email protected] J. ZHANG is with the Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China and also with the Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China. Manuscript submitted March 13, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
However, the requirements regarding high-temperature strength and hot corrosion resistance might come into conflict. For hot corrosion resistance, Cr is important since it can produce a protective Cr2O3 scale which is the most resi
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