Study On The Preparation Of Ni-based Coating With Nanoα-Al₂O₃ As Dispersion Phase And Its Abrasive Resistance

The preparation of Ni-coated composite powders and the remix of the Ni-based powders and the coated powders were studied. Well abrasive resistance Nano-Al2O3-metal composite coating was prepared by flash thermal spray method and its abrasive wear property was studied.The preparation of Ni-coated Nano-Al2O3 was studied in this article. First a layer of nickel precursor was precipitated on the Nano-Al2O3 particles by nonhomogenous precipitation and then the nickel precursor coated powders were calcinated and reduced to prepare the Ni-coated Nano-Al2O3 composite powders. The Ni-coated Nano-Al2O3 powders (simplified as coated powder) were characterized using several techniques such as XRD, SEM,EDS and TEM to determine particle size, composition, phase and morphology. The effects of the disperse condition (dispersant type, ultrasonic vibration and mechanical stirring, the Nano-Al2O3 powder dispersion status), reagent concentration, mixed style of the precipitator and the reagent were studied. The key to prepare coated powder was to get well-dispersed Nano-Al2O3 suspension and get the Ni-precursor precipitated on the Nano-Al2O3 particles rather than spontaneous nucleation. The results indicated that the use of the freshly prepared Nano-Al2O3, using the PEG400 as dispersant, lower reagent concentration and ultrasonic vibration and mechanical stirring could improve the disperse property of the Nano-Al2O3 in the solution. Slowly dripped the precipitator into the reagent suspension made it possible for the nickel precursor precipitated on the Nano-Al2O3 rather than spontaneous nucleation.The remix of the coated powder and the Ni-based powder and preparation and abrasive resistance of the coating were studied. The Nano-Al2O3-metal composite coating was prepared by flash thermal spray method and it was abraded on abrasive wear machine to study its abrasive resistance property. The effects of different surfactants on the stability of the remixed suspension were studied. The effect of the volume fraction of the Nano-Al2O3 on the coating preparation technique and the abrasive resistance ability of it were studied. The effect of the size and the coated status of the Al2O3 on the abrasive wear property of the coating were also studied. With 2vol% addition of Nano-Al2O3 the coating had the best abrasive wear resistance property and was twice of the pure Ni-based powder coating. With the same additive volume the abrasive resistance of the coating increased as the size of the dispersion strengthening phase decreases; the abrasive wear resistance property of the coating strengthened by the coated Nano-Al2O3 was better than by the uncoated powder. The coated Nano-Al2O3 improved the wetting property of the Nano-Al2O3 in the Ni-based coating and improved the abrasive resistance of the coating. SEM study showed that the Ni-coated Nano-Al2O3 dispersed well in the coating.