Cyclic Oxidation Properties of the Nanocrystalline AlCrFeCoNi High-Entropy Alloy Coatings Applied by the Atmospheric Plasma Spraying Technique

Farzin Ghadami,Soheil Ghadami,Mohammad Amin Davoudabadi

doi:10.3390/coatings12030372

Farzin Ghadami, Soheil Ghadami + Show 1 more

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https://doi.org/10.3390/coatings12030372

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Abstract

Microcrystalline and nanocrystalline AlCrFeCoNi high-entropy alloy (HEA) coatings were applied on Inconel 718 superalloy using the atmospheric plasma spraying (APS) process. The high-temperature oxidation behavior of the microcrystalline and nanocrystalline AlCrFeCoNi HEA-coated superalloy was examined at 1100 °C under the air atmosphere for 50 cycles under cyclic heating and cooling (1 h for each cycle). The oxidation kinetics of both nanocrystalline- and microcrystalline-coated superalloys were accordingly analyzed by weight change measurements. We noted that the uncoated and coated samples followed the parabolic rate law of the oxidation. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDS), elemental mapping and X-ray photoelectron spectroscopy (XPS) were used to analyze the oxidized coated and uncoated samples. In the HEA-coated superalloy, Fe, Ni, Co and Al were oxidized in the inter-splat region, whereas the splats, which consisted mainly of Ni and Cr, remained unoxidized. Due to the formation of compact and adhesive thin NiO, CoO oxides and spinels together with the Al2O3 oxide scale on the surface of the coating during oxidation, the developed nanocrystalline HEA coating showed better oxidation resistance compared with the microcrystalline HEA coating.

Highlights

High-entropy alloys (HEAs) are a new category of metallic alloys that demonstrate brilliant characteristics
Despite working on advanced materials and ceramics starting in the 1990s [2–6], the development, testing and application of advanced HEAs and their coatings have been the focus of the research efforts since the mid-2010s [7–9]
The Inconel 718 superalloy was chosen as the base material for deposition of the micro- and nanocrystalline HEA coatings, which is the most preferred choice for the hot section of gas turbine engine components and other structural applications, as it works in high temperature, aggressive environments and has excellent mechanical properties and high-temperature phase stability

Summary

Introduction

High-entropy alloys (HEAs) are a new category of metallic alloys that demonstrate brilliant characteristics. These types of materials are useful candidates for the design and manufacturing of innovative engineering parts and equipment in different kinds of bulk, sintered, as-cast and coating forms to resist harsh industrial environments [1]. Owing to the various primary metallic alloys with an equimolar or near-equimolar composition, HEAs have prominent chemical, mechanical and thermal properties, including higher mechanical strength and hardness, greater chemical stability, better corrosion and oxidation resistance and outstanding wear behavior. HEA compositions have been recently utilized as thermoelectric high-performance magnets, new generation catalysts and advanced superconductors.

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