Mechanical behavior, tribological properties, and thermal stability of (AlCrNbSiTiVZr)N high entropy alloy nitride coatings and their application to Inconel 718 milling

(AlCrNbSiTiVZr)N high entropy alloy nitride coatings were deposited on silicon wafers and WC substrates using a radio-frequency magnetron sputtering system with nitrogen flow rates of 0, 10, 15, and 20 sccm (coating codes: N0, N10, N15, and N20, respectively). The coatings were subsequently annealed in a vacuum at 950 °C for 1 h (coating codes: HN0, HN10, HN15, and HN20). The effects of the nitrogen flow rate on the composition, microstructure, mechanical properties, and tribological properties of the coatings were systematically examined. The N0 and N10 coatings had amorphous structures, whereas the N15 and N20 coatings had FCC structures. Among the as-deposited coatings, the N20 coating exhibited excellent mechanical properties and a superior tribological performance. All the annealed coatings showed an FCC structure and formed a V₂O₅ solid lubricant layer in ball-on-disk sliding tests. The lubricant layer reduced the coefficient of friction and led to a smooth friction curve. The annealed coatings additionally showed a high hardness, good adhesion strength, and excellent thermal stability. The mechanical and tribological properties of the HN20 coating were particularly impressive. In Inconel 718 milling trials, the N20-coated cutter showed an excellent machining performance, with significantly reduced flank wear, notch wear, and built-up edge adhesion.