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Two kinds of layered double hydroxides inhibition materials were synthesized on graphene oxide, and applied to strengthen the Ni-based coating on Mg-Li alloy. The composition and release properties of corrosion inhibition materials were studied. The formation of passivated film and the corrosion resistance mechanism of coating were summarized. The results show that two kinds of corrosion inhibition materials had good release properties. The addition of corrosion inhibition materials was helpful to form Ni-based composite coatings with fine and dense cell clusters, which strengthened the corrosion resistance of the coating, especially for a long time. • Two kinds of graphene-based corrosion inhibition materials were synthesized. • Corrosion resistance of Ni-based coatings in different soaking time was studied. • Inhibition materials enhanced the corrosion resistance of coatings on Mg-Li alloy. • Passivation film formation and corrosion resistance mechanism were studied. [ABSTRACT FROM AUTHOR]

For the application of lightweight alloys, the corrosion and wear problems of magnesium-lithium (Mg-Li) alloys have always been important problems that cannot be ignored. The coupling protection of multiple technologies has gradually become a new trend. In this study, layered double hydroxides (LDH) nanosheet arrays were in-situ grown on Ni-P coating by the electroless plating technology combined with hydrothermal synthesis technology. The optimum deposition conditions (temperature-time-pH) were selected by orthogonal test. The surface morphology, structure, corrosion resistance and wear resistance of LDH/Ni composite coatings under different conditions were systematically studied by SEM, XRD, FT-IR, DSC, electrochemical and tribological tests. The growth mechanism of LDH suitable for Ni-P coating surface was proposed by analyzing the growth process of LDH nanosheet arrays. The results showed that the condition of 125 °C-12 h-13 was conducive to the growth of LDH nanosheet arrays. Compared with the Ni-P coating and the composite coating under other conditions, the LDH 125°C-12h-13 /Ni composite coating has the lowest self-etching current density (7.50 × 10−7 A·cm−2) and the average friction coefficient (0.35). The defect sealing effect and Cl− barrier property of LDH effectively improved the corrosion resistance of the coating. The frictional properties were improved by lubrication and heat absorption properties of LDH. In addition, it was found that the growth of LDH on the Ni-P coating surface followed the mechanism of "deposition nucleation-diffusion growth". • Nanosheet arrays in-situ coupled Ni-based coatings on Mg-Li alloy were prepared. • Optimum growth conditions of nanosheet arrays were selected by orthogonal test. • The composite coating had better corrosion and wear resistance for Mg-Li alloy. • Wear mechanism and growth mechanism of LDH nanosheet arrays were studied. [ABSTRACT FROM AUTHOR]

In this study, graphite/CeO 2 reinforced Co-based coatings were prepared on the surface of HT250 gray cast iron by the plasma cladding technology. The influence of graphite and CeO 2 on microstructure and properties of Co-based coatings were studied in detail. The phase composition and microstructure of coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The micro-hardness, wear resistance and corrosion resistance of coatings were evaluated using micro-hardness tester, friction wear testing machine and electrochemical workstation. The results showed that the addition of graphite was beneficial to enhance micro-hardness and wear resistance of coatings, but there was still shortcoming in improving corrosion resistance. On this basis, CeO 2 was further introduced together with graphite. The microstructure of coatings was found to be more uniform under the synergy of graphite and CeO 2. The micro-hardness increased from 684.5 HV 0.3 (coatings adding graphite alone) to 767.4 HV 0.3 (coatings adding graphite and CeO 2), which was 29.7% and 115.1% higher than that of as-cladded coatings and substrate respectively. More importantly, the corrosion current density of coatings was an order of magnitude lower than that of coatings adding graphite alone. Therefore, adding CeO 2 together with graphite was beneficial to the synergistic improvement of micro-hardness, wear resistance and corrosion resistance of Co-based coatings. • Co-based coatings adding graphite/CeO 2 were prepared by plasma cladding. • The microstructure of coatings became uniform after adding graphite/CeO 2. • Wear resistance of coatings adding graphite together with CeO 2 was enhanced. • Corrosion resistance of coatings adding graphite together with CeO 2 was raised. [ABSTRACT FROM AUTHOR]

An ablation resistant coating with self-transpiration cooling effect was prepared on the surface of aluminum alloy by dilution effect of high speed laser cladding. The coatings mainly contain ablation resistant phases ZrB 2 and SiC, and low-melting phases Al and Al 3.21 Si 0.47. The ablation property of coatings was investigated at different heat fluxes (35.39, 70.77, 106.16, 141.54) MW⸱m−2. The mass ablation rate increased gradually, and the morphology of ablation region changed significantly with the increased heat flux. The self-transpiration cooling effect of coatings was studied by phase, morphology, and element distribution of ablation region. The self-transpiration cooling effect weakened the oxidation behavior of ZrB 2 and SiC at heat fluxes of 35.39 and 70.77 MW⸱m−2 and protected the coating from being exhausted when the heat fluxes were 106.16 and 141.54 MW⸱m−2. [ABSTRACT FROM AUTHOR]

In this work, the CoCrFeNiNbx (x: molar ratio, x = 0.45, 0.5, 0.75, and 1.0) high entropy alloy coatings were synthesized on a 304 stainless steel substrate by laser cladding to investigate the effect of Nb element on their microstructure, hardness, and wear resistance. The results indicated that in all of the CoCrFeNiNbx alloy coatings, two phases were found: One was a face-centered cubic (FCC) solid solution phase, the other was a Co1.92Nb1.08-type Laves phase. The microstructures of samples varied from hypoeutectic structure (x = 0.45 and 0.5) to hypereutectic structure (x = 0.75 and 1.0). The Vickers hardness of CoCrFeNiNbx alloy coatings was obviously improved compared with the substrate. The hardness value of the CoCrFeNiNb1.0 alloy coating reached to 590 HV, which was 2.8 times higher than that of the substrate. There was also a corresponding variation in wear properties with hardness evolutions. Wherein the hypereutectic CoCrFeNiNb1.0 alloy coating with the highest hardness exhibited the best wear resistance under the same wear condition, the dry wear test showed the wear mass loss of CoCrFeNiNb1.0 alloy coating was less than a third of the substrate. The high hardness and wear resistance properties were considered with the fine lamellar eutectic structure and proper combination of FCC and Laves phases. [ABSTRACT FROM AUTHOR]

As reinforcements, carbonaceous nanomaterials (CNMs) especially multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO), have attracted increasing attention in the application of electrodeposition. In this work, Ni-based nanocomposite coatings with MWCNTs and GO were prepared by electro-brush plating technique (EBP). The results showed that adding MWCNTs and adding GO both significantly improved the compactness of Ni coatings, however, the latter contributed more uniform microstructure and morphology of nanocomposite coatings owing to the excellent dispersion of GO. In addition, MWCNTs and GO could not only provide numerous nucleation sites for Ni primary crystals contributing the grain refinement, but also co-deposited with Ni atoms to form a strong interfacial bonding with Ni matrix. The addition of MWCNTs and GO can significantly reduce the worn volume of coatings from 7.52 × 107 μm3 to 3.49 × 107 μm3 and 2.82 × 107 μm3, respectively. Moreover, Ni nanocomposite coatings adding GO exhibited better wear resistance and friction stability than that of adding MWCNTs. Microstructural characterizations revealed that during wear testing, the agglomerated MWCNTs in nanocomposite coatings were destroyed severely and transformed into the shorten MWCNTs or the unfolded sidewalls, thereby leading to the instability of the wear process. In contrast, the damage degree of rGO was relatively slight. The nanosheets of rGO uniformly distributed in nanocomposite coatings became smaller and some of them were stacked between each other, which promoted the stability of friction process. Image 1 • Comparison study of MWCNTs and GO reinforced Ni composite coatings was conducted. • Both MWCNTs and GO significantly improved the compactness of pure Ni coatings. • HRTEM characterization provided evidences for grain refinement of MWCNTs and GO. • Adding GO promoted the stability of friction process compared with MWCNTs. • Structural variations of MWCNTs and GO after wear testing were investigated. [ABSTRACT FROM AUTHOR]