High Entropy Hardmetals in Thermal Spray Coatings
Surface characteristics materials have an impact on how well they perform in industrial applications. Surface modification technologies are so widely available, that became economically feasible the replacement of a subpar base material with a coating providing better surface properties and performance, especially in corrosive environments or severe stress applications. In the line-of-sight process known as thermal spraying, feedstock material (which can be in the form of powder, wire, rod, or suspension) is fed into a spray torch, heated to a molten or nearly molten state, and then accelerated toward a base material. Thermal spraying coatings have evolved into innovative developments in the field of industrial progress, improving the effectiveness and durability of various materials. In the industrial coatings industry, an innovative development has appeared: High Entropy Alloys or HEAs. This heightened scientific interest is also depicted in research community as the latest years, an increment presented in the total citations per year of research articles on HEA thermal spray coatings that have been published in peer-reviewed journals (Meghwal, A., 2020).
Understanding High Entropy Alloys (HEAs)
High-Entropy Alloys (HEAs) are an exciting new category of materials with distinctive traits and properties that are showing promise as thermal spray coatings for challenging environments. HEAs are being used as feedstock for coating processes more frequently as a result of reports highlighting their exceptional qualities in both bulk and coating forms. Research in this area has advanced due to recent discoveries that thermal sprayed HEA coatings perform better than traditional materials. In contrast to conventional alloys, HEAs contain a mixture of several different elements in nearly equal quantities, creating a high-entropy state where disorder predominates at the atomic level. This high entropy state results in the formation of an intricate atomic structure with a wide range of mechanical, thermal, and chemical properties.
The Main Properties of HEAs & Thermal Spray Coating applications
High entropy alloys (HEAs), specifically high entropy hard metals, have several unique characteristics that distinguish them from conventional alloys. They can withstand high temperatures and maintain stability in challenging conditions due to their high melting points. The random arrangement of their atoms reveals their exceptional mechanical strength and high resistance to wear and deformation. Additionally, the chemical makeup of HEAs can be precisely adjusted to develop specific properties, increasing their adaptability for a variety of applications. Their remarkable thermal stability makes them ideal for thermal spray applications since they maintain their properties in heat stress. Additionally, the precise tunability of HEAs enables property customisation, enhancing their suitability for a variety of applications. This adaptability is essential for sectors like aerospace, energy, and the automotive, where HEAs are leading performance and longevity advancements. The vast potential of HEAs is being explored by scientists and engineers, from industrial machinery to aerospace components, where their adaptability and robustness are reshaping the future of engineering and materials (Rogachev,2020).
Applications Across Industries
HEAs have made significant progress in several industries. The use of HEAs into vehicle components has revolutionised the automotive manufacturing industry by offering materials that are remarkably durable and lightweight. This invention promotes a new era of robust and effective cars by improving vehicle performance, longevity, and safety while lowering maintenance needs (Zhang, Y., 2022), (Xin W.,2020). The application of HEAs over commercial alloys in the gas industry is also being studied. The use of these alloys in natural gas transmission pipelines is being researched because of their strong corrosion resistance under extreme conditions (Rodriguez, 2018). In steel industry, the use of HEAs results in producing steel parts with higher strength hardness, and wear resistance. This contributes to manufacturing more durable and high performance steel products suitable for demanding applications in infrastructure, machinery, construction (Abhijith, 2022). These different applications of High Entropy Alloys (HEAs) in automotive, steel and oil & gas, demonstrate their adaptability. HEAs continue to drive innovation and hold great potential to have a big impact on a lot of different industrial sectors as more research is done to discover their special qualities.
Looking Forward: Challenges and
HEAs face challenges during their journey in thermal spray coatings. Researchers are meticulously exploring new alloy compositions and improving production methods. More specifically, in thermal spray, the coatings used are composed of toxic and critical materials (i.e., Tungsten Carbide (WC)-Cobalt (Co) and Chromium VI). As an alternative to those conventional materials used for coating, CoBRAIN will find novel formulations by utilising the versatility and low environmental impact of thermal spray to produce alloy and hardmetal coatings free of toxic and critical materials. CoBRAIN aims to introduce two new material classes to the coating market: 1) crystalline High Entropy Hardmetals and 2) amorphous High Entropy Hard Metals. To achieve this, the project will utilise established technologies that are currently in use at the industrial level. Exciting opportunities lie in the future, from cutting-edge coating techniques to the discovery of new applications across industries.
In conclusion, the development of High Entropy Alloys (HEAs) is a promising step forward for material science, especially for thermal spray coatings. These alloys represent the cutting edge of surface modification technology thanks to their distinctive atomic structure and wide range of mechanical, thermal, and chemical properties. In industries like automotive, steel and oil & gas, their exceptional mechanical strength, remarkable thermal stability, and resistance to wear and deformation make them a game-changer. Engineers and researchers are reshaping the future of materials across sectors by utilising the robustness and adaptability of HEAs to create high-performance, long-lasting components that improve efficiency, reliability, and longevity. Their potential to completely transform industrial applications is still a compelling driving force for scientific and technological advancements, as research into the full range of HEA capabilities is still ongoing.
Meghwal, A., Anupam, A., Murty, B.S. et al. Thermal Spray High-Entropy Alloy Coatings: A Review. J Therm Spray Tech 29, 857–893 (2020). https://doi.org/10.1007/s11666-020-01047-0
Rogachev, A.S. Structure, Stability, and Properties of High-Entropy Alloys. Phys. Metals Metallogr. 121, 733–764 (2020). https://doi.org/10.1134/S0031918X20080098
Zhang, Y., Wang, D., Wang, S., High-Entropy Alloys for Electrocatalysis: Design, Characterization, and Applications (2022). https://doi.org/10.1002/smll.202104339
Xin W., Wei G., Yongzhu Fu., High-entropy alloys: emerging materials for advanced functional applications. Journal of Materials Chemistry A (2020). https://doi.org/10.1039/D0TA09601F
Abhijith, N.V., Kumar, D. & Kalyansundaram, D. Development of Single-Stage TiNbMoMnFe High-Entropy Alloy Coating on 304L Stainless Steel Using HVOF Thermal Spray. (2022). https://doi.org/10.1007/s11666-021-01294-9
Rodriguez, Alvaro A., Tylczak, Joseph, and Margaret Ziomek-Moroz. “Corrosion Evaluation of CoCrFeMnNi High-Entropy Alloys (HEAs) for Corrosion Protection of Natural Gas Transmission Pipelines.” Paper presented at the CORROSION 2018, Phoenix, Arizona, USA, (2018).