Cold sprayed AlNiCoFeCr–TiB2 metal matrix composite coatings

Abstract

In this work, the mechanically alloyed AlNiCoFeCr high entropy alloy (HEA) was used as matrix to develop metal matrix composite (MMC) coatings. Dense and thick AlNiCoFeCr – 30 wt % TiB2 MMC coatings were firstly fabricated by solid-state cold spraying (CS) technique at the low pressure of 0.9 MPa, and temperature of 300 and 450 °C. The effect of compressed air flow temperature and pressure parameters on structure and mechanical properties of coatings were established. As a low-temperature deposition process, CS completely retained the phase composition and nanostructure in the coatings without any phase transformation. With an increase in pressure up to 0.9 MPa a refinement of the coating structure and a double increase in the fraction of TiB2 particles in the coating were detected. An increase in temperature at least to 300 °C breaks down the oxide layers of the particles, multiplying the deposition efficiency and the properties of the coatings. The coatings fabricated at a spraying temperature of 450 °C and a compressed air flow pressure of 0.9 MPa exhibit the average thickness of 1110 μm, as well as a good combination of high microhardness (6.9 GPa) and sufficient indentation fracture toughness (3.8 MPa∙m1/2).