Microstructure and Corrosion Behavior of Atmospheric Plasma Sprayed NiCoCrAlFe High Entropy Alloy Coating.

Kashif Mehmood,Rabeeka Firdous,Humaira Kousar,Muhammad Ilyas,Muhammad Usman,Malik Adeel Umer,Muhammad Imran,Ahmed Umar Munawar,Muhammad Shahid

doi:10.3390/ma15041486

Kashif Mehmood, Rabeeka Firdous + Show 7 more

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https://doi.org/10.3390/ma15041486

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Abstract

High entropy alloys (HEAs) are multi-elemental alloy systems that exhibit a combination of exceptional mechanical and physical properties, and nowadays are validating their potential in the form of thermal sprayed coatings. In the present study, a novel synthesis method is presented to form high entropy alloy coatings. For this purpose, thermal sprayed coatings were deposited on Stainless Steel 316L substrates using atmospheric plasma spraying technique with subsequent annealing, at 1000 °C for 4 h, to assist alloy formation by thermal diffusion. The coatings in as-coated samples as well as in annealed forms were extensively studied by SEM for microstructure and cross-sectional analysis. Phase identification was performed by X-ray diffraction studies. The annealed coatings revealed a mixed BCC and FCC based HEA structure. Potentiodynamic corrosion behavior of SS316L sprayed as well as annealed coatings were also carried out in 3.5% NaCl solution and it was found that the HEA-based annealed coatings displayed the best corrosion resistance 0.83 (mpy), as compared to coated/non-annealed and SS 316 L that showed corrosion resistance of 7.60 (mpy) and 3.04 (mpy), respectively.

Highlights

Accepted: 4 January 2022High entropy alloys (HEAs) have been gaining ample attention since 1996 whenYeh et al introduced the concept of multi-element alloy and published in 2004 [1], Later on, Cantor et al named them ‘multi-component alloys’ in the same year [2]
Corrosion resistance studies are unavoidable for their prospective application in some mediums especially in saline medium (3.5% NaCl) as the corrosion behavior of HEAs is comparatively unfamiliar
SEM image revealed that the resultant microstructure was homogenized and the coatThe SEM image revealed that the resultant microstructure was homogenized and ings have well adhered to the substrate with little porosity

Summary

Introduction

Accepted: 4 January 2022High entropy alloys (HEAs) have been gaining ample attention since 1996 whenYeh et al introduced the concept of multi-element alloy and published in 2004 [1], Later on, Cantor et al named them ‘multi-component alloys’ in the same year [2]. 5% and 35% and result in enhanced features such as mechanical strength, nanoprecipitation [4,5], extra-ordinary corrosion resistance [6], high resistivity, and magnetism [7]. These properties could be tailored further by varying and adjusting the elemental compositions that make them even more fascinating materials [6]. In addition to being a potential candidate for functional and structural materials, NiCoCrAlFe HEAs can be applied as a surface coating to protect against corrosion and increase the durability of the material. In addition to traditional casting and forging methods, various thermal spraying techniques have been employed to coat HEAs on the substrate, firstly, high-velocity oxy-fuel (HVOF) [8,9] technique in which a specially designed torch allows the compressed

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