Mechanical properties and corrosion resistance evaluation of nanocomposite AlCrNbSiTiBCN high entropy alloy coatings fabricated using superimposed HiPIMS-MF system: Effect of B contents

The rapid development of compositionally complex alloys, such as multicomponent ceramics in bulk quantities, is challenging due to their chemical complexities. Physical vapor deposition is one method that facilitates such development using a single multi-principal element alloy target or multiple targets. In this study, a superimposed high power impulse magnetron sputtering system with mid-frequency pulses (HiPIMS-MF) was used to fabricate five nanocomposite AlCrNbSiTiBCN high entropy alloy nitride coatings in a reactive gas chamber with varying B contents from a DC-powered TiB₂ target. The coatings exhibited nanocomposite microstructure consisting of nano-sized FCC metal nitride phases with small amounts of carbide and carbonitrides embedded in the amorphous matrix. The hardness decreased from 19.9 to 15.9 GPa with increasing B contents in the form of an amorphous BN matrix with hexagonal short-range order. The coatings showed slight variations in wear resistances ranging from 1.1 × 10^–5 to 6.1 × 10^–5 mm³N^-1m^-1 except for the coating with the highest B content, which had a significant wear rate increment reaching up to 1.8 × 10^–4 mm³N^-1m^-1. All coatings show excellent corrosion resistance in 3.5 wt. % NaCl aqueous solution with very high polarization resistance values, which are 16 to 37 times higher than the bare AISI304 stainless steel substrate. This study successfully developed promising hard and anticorrosion AlCrNbSiTiBCN high entropy alloy nitride coatings suitable for surface and interface modification of materials for advanced or engineered applications.