Preparation and Tribological Properties of Ni−Al2O3−PTFE Composite Coatings for Rotor Shaft
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Graphical Abstract
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Abstract
Aiming at the drawback of short repair intervals of domestic aviation transmission systems, the hard particles Al2O3 and lubrication material PTFE were used as particles, employed with the brush plating technology to prepare Ni−Al2O3, Ni−PTFE and Ni−Al2O3−PTFE composite coatings on the surface of T2 copper sheet, which is a commonly used transition layer metal material on the rotor shaft. Scanning electron microscopy and microhardness instruments were employed to characterize and analyze the microstructure, element content distribution, and hardness of the coatings. The friction and wear tests on the coated samples were conducted with a self-made pin plate friction and wear testing machin to explore the frictional properties and wear mechanism of the coating. The results show that with the increase of Al2O3 particle content, the surface microcrystalline unit size of Ni−Al2O3−PTFE decreases and the microhardness increases. The maximum microhardness of Ni−Al2O3−PTFE (3∶1) is 236 HV, which is about 66% higher than that of Ni−PTFE composite coating. The Ni−Al2O3−PTFE composite coating combines the advantages of Al2O3 and PTFE, which not only reduces friction, but also has excellent wear resistance. The anti-friction performance of Ni−Al2O3−PTFE (1∶1) composite coating is the best, with a friction coefficient reduction of about 52% compared to Ni−PTFE composite coating. The wear resistance of Ni−Al2O3−PTFE (3∶1) composite coating is the best, and its wear rate is reduced by about 85% compared to Ni−PTFE composite coating. The wear form of Ni−Al2O3−PTFE composite coating is mainly mechanical wear, with slight oxidative wear and adhesive wear. The micro-convex plastic deformation on the surface of composite coating can provide a lubrication film for the friction surface, of which PTFE is a self-lubricating particle, and Al2O3 particles play a role in supporting and strengthening the coating, preventing the coating from wear.
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