Abstract
The present work investigates the hot corrosion behavior of Al0.1CoCrFeNi high entropy alloy (HEA) and Ni-base Alloy 718. Electrochemical tests were conducted to characterize the corrosion behavior of Al0.1CoCrFeNi HEA and Alloy 718 in a molten Na2SO4-NaCl eutectic mixture at 750 ± 5°C in the presence of a platinum catalyzed SO2/air mixture. The morphology of the surface of Al0.1CoCrFeNi HEA and Alloy 718 was investigated using scanning electron microscopy (SEM) as well as energy dispersive spectroscopy (EDS). The results indicate that the polarization resistance of the HEA was higher and the corrosion rate lower in comparison with Alloy 718. SEM and EDS analyses reveal the formation of a dual oxide layer on the HEA that provides a better corrosion barrier compared to the single chromia scale observed on Alloy 718.
Highlights
IntroductionThe random arrangement of multiple elements in solid solutions results in a particular locally-disordered chemical environment, which is expected to result in unique properties.[3] the literature is sparse in regard to the stability of these alloys in corrosive environments, e.g. in molten salts
high entropy alloys (HEAs) contain five or more elements with equal or near-equal amounts.[1,2]. This unconventional alloying (Figure 1) strategy results in HEAs with attractive properties, e.g., wear resistance, hardness and high temperature strength coupled with relatively low density and multiple elements that could participate in passive film formation
The average open circuit potential (OCP) values recorded at the 60th minute are −897 ± 39 mV (N = 3, where N represents the number of replicates) and −701 ± 227 mV (N = 4) for the HEA and Alloy 718, respectively
Summary
The random arrangement of multiple elements in solid solutions results in a particular locally-disordered chemical environment, which is expected to result in unique properties.[3] the literature is sparse in regard to the stability of these alloys in corrosive environments, e.g. in molten salts. The aim of the present work was to evaluate the corrosion behavior of an Al0.1CoCrFeNi HEA in a molten salt environment and benchmark it to a conventional Ni-base superalloy, Alloy 718, that is used in aircraft engines. Available potentiostat.[6] The testing procedure involved recording the open circuit potential (OCP) for one hour. This was followed by a linear polarization (LP) scan from −20 to +20 mV relative to the OCP at a scan rate of 1 mV/s. The test coupons were metallographically prepared to a 1 μm surface finish and analyzed using scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS)
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