Abstract: The high-speed friction and wear performance of the electrospark deposited AlCoCrFeNi high entropy alloy coating was investigated by taking conventional electroplated hard Cr coating as comparison. The nanoindentor and friction and wear testing machine were employed to test the nano-mechanical properties and friction coefficient of the coatings. Furthermore, scanning electron microscopy (SEM), transmission electron microscope (TEM), energy dispersive X-ray spectrum (EDS) and X-Ray Diffraction (XRD) were adopted to analyze the microstructure, composition and phase structure of the coatings. The results indicated that the AlCoCrFeNi coating exhibited fine grains and compact structure without cracks and consisted of BCC and FCC phases. There were an approximate 10% increase in hardness, a 8% decrease in elasticity modulus, a higher values of H/E and H3/E2 of the AlCoCrFeNi coating, compared with the hard Cr coating. The steady friction coefficient of the AlCoCrFeNi coating was only 0.25—0.33, while the hard Cr coating was 0.65—0.73, when the quenched GCr15 steel ball was used as one of the friction pair under the load of 10 N, the reciprocating travel of 10 mm and the velocity of 800 r/min. AlCoCrFeNi coating showed about 41% reduction in wear rate compared with hard Cr coating. The wear mechanism of the hard Cr coating is mainly characterized as adhesive wear, and the failure mode can be attributed to spalling caused by crack propagation, whilst the wear mechanism of the AlCoCrFeNi coating primarily belongs to micro-cutting abrasive wear and oxidation wear, and the oxide film formed in the course of friction and wear contributed to the wear resistance of the AlCoCrFeNi coating. In conclusion, the AlCoCrFeNi coating presents better high-speed friction and wear performance than the hard Cr coating.
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