Oxidation Behaviour of HVAF Sprayed Al0.3CrFeNiTi0.3 High Entropy Alloy Coating

Abstract

This study investigates, for the first time, the oxidation resistance of a novel Al 0.3 CrFeNiTi 0.3 high-entropy alloy (HEA) coating produced via high velocity air fuel (HVAF) spray, examined by isothermal oxidation at 500, 700 and 900 °C for up to 200 h. The oxidation rate coefficient ( k h ) was determined by measuring the change in thermally grown oxide (TGO) layer thickness and converted to an approximate mass-based coefficient ( k p ) for easier comparison to oxidation resistant materials. XRD and SEM/EDS analysis determined the phase and microstructural characteristics of the coating. The oxidation testing at 500 °C indicated negligible surface oxidation, however, at 700 and 900 °C, the coating formed a complex, multilayered, TGO layer, comprised of Al 2 O 3 , Cr 2 O 3 and a mix of TiFe 2 O 4 and NiFe 2 O 4 spinel oxides. The calculated oxidation rate coefficients ( k p ) of 9.6x10 −14 and 1.1x10 −12  g 2 /cm −4  s −1 at 700 and 900 °C, respectively.