Nanostructural AlNiCoFeCrTi High-Entropy Coatings Performed by Cold Spraying

Abstract

In this study the high-entropy alloy (HEA) coatings was sprayed by cold spraying (CS) method on steel substrate from AlNiCoFeCrTi HEA powder fabricated by short-time mechanical alloying (MA) and annealing. It was determined that in the MA of powder mixture forming metastable nanostructured bcc solid solution which changes to ordered bcc solid solution (B2 phase) after annealing and vice versa after additional grinding. Also after annealing AlNiCoFeCrTi HEA powder contains intermetallic σ-phase and TiC particles which retain in powder after its grinding. So, before deposition the feedstock powder consists of disordered bcc solid solution, an intermetallic σ-phase, and TiC carbide. Mean thickness of deposited coatings is about 450 μm. Due to low temperature of CS process, AlFeNiCoCrTi coating has same phase composition and nanostructural state as a feedstock powder. The Vickers hardness of AlFeNiCoCrTi HEA coating is 10.3±0.3 GPa. Coating has very low porosity (<1%) and good adhesion to the steel substrate. High strength characteristics of the coating are provided by the high characteristics of feedstock powder and its strengthening mechanisms, as well as impact hardening during spraying at a supersonic speed at low temperature.