Low temperature hot corrosion screening of single crystal superalloys

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2018-10-25

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MDPI

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Article

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1996-1944

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James L. Smialek and Simon Gray. Low temperature hot corrosion screening of single crystal superalloys. Materials, 2018, Volume 11, Issue 11, Article number 2098

Abstract

Single crystal superalloys were screened in Type II molten (Na,K)-sulfate hot corrosion re-coat tests in air +300 ppm SO2 at 700 °C. They exhibited large 20–40 mg/cm2 weight changes, repeated spallation, and non-protective, 25–50 μm thick corrosion layers after 300 h of testing. Scale cross sections revealed dual outer Ni(Co)O and inner Al(Cr)S-rich corrosion layers. This chemical differentiation was partially consistent with previous models of oxide fluxing, alloy sulfidation, NiO micro-channel diffusion, and synergistic dissolution mechanisms. Broad shallow pits or uniform attack morphologies were consistent with prior studies performed in high >100 ppm pSO2 environments. Higher Mo experimental alloys trended toward more degradation, producing 100 μm thick scales with distinct Al(Cr)S-rich inner layers or 500 μm thick NiO. The aggressive behavior in these environments supports the need for LTHC-resistant coatings for single crystal superalloys.

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Github

Keywords

Type II hot corrosion, single crystal superalloys, molten salt

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Attribution 4.0 International

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