Novel candidate of metal-based thermal barrier coatings: High-entropy alloy

Abstract

To obtain compatible properties of low thermal conductivity and high thermal stability, Al0.6CoCrFeNiTi high-entropy alloy was designed as a novel candidate of metal-based thermal barrier coatings (MBTBCs). The corresponding high-entropy alloy coatings were fabricated by both high-velocity oxygen-fuel spraying (HVOF) and atmospheric plasma spraying (APS), and then the dependence of thermal insulation properties on microstructure was investigated. The both coatings exhibit a simple body-centered cubic (BCC) structure, but present obvious difference in microstructure and defect characters which relates to the evolution of in-flight particles. Benefit from the extremely low thermal conductivity, the APS-deposited coating can increase 13.24 °C of the surface temperature of piston crown and yield a temperature reduction of 19.00 °C along the thickness direction, which mean a positivity on enhancing the power efficiency of vehicle engines without sacrificing the strength of aluminum alloy components. In virtue of a decoupling method, the crucial effect of microstructure on thermal conductivity is disclosed, thus interpreting the excellent thermal insulation property of APS-deposited coating dominated by grain refinement and disordered BCC structure. The present results demonstrate a great potential of high-entropy alloy coatings as thermal barrier application and provide an inspiration for future works aiming to design these coatings to meet specific engineering needs.