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Ni-W-P ternary coating was synthesised on AZ91D magnesium alloy substrates by an integrated method. The corrosion resistance mechanism of conversion film-electroless Ni-W-P coatings on a substrate ...

The purpose of this work is to investigate the microstructure and mechanical properties of a novel WC-reinforced Co matrix composite coating synthesized by pulse electrodeposition technique with va...

A novel Co-WC composite coating was deposited on the surface of high speed steel (HSS) substrate by an energy-efficient method of electrodeposition. The effects of process parameters on friction and wear properties of the composite coatings were evaluated, and the worn morphologies of Co-WC composite coatings were investigated by scanning electron microscopy. Results revealed that the incorporation of WC particles can significantly improve the wear resistance of the coating. As the current density was increased to 6.5Adm-2 and the WC concentration was increased to 35g/L, the Co-WC composite coating had the lowest friction coefficient and wear loss.

A kind of corrosion-resistant Ni-Mo-P composite coating was deposited on the surface of AZ91D magnesium alloy substrate by electroless plating method with different concentration of Ce(NO3)3 and Nd(NO3)3. The deposition mechanism of Ni-Mo-P composite coating was explored. Furthermore, the effects of Ce(NO3)3 and Nd(NO3)3 concentration on the microstructure and properties of Ni-Mo-P composite coatings were studied. Results indicated that the Ni-Mo-P composite coatings prepared by adding the optimal concentration of Ce(NO3)3 and Nd(NO3)3 had few defects. Meanwhile, the deposition rate of the composite coatings and the adhesion between the coating and the magnesium alloy substrate were improved. When the concentration of Ce(NO3)3 and Nd(NO3)3 were 0.10 and 1.00 g/L, the Ni-Mo-P composite coatings had the minimum corrosion rate of 0.826 and 0.681 g/m2·h, respectively. Herein, compared with the addition of Ce(NO3)3, the Nd(NO3)3 added Ni-Mo-P composite coating has the maximum arc radius of capacitive resistance and significant improvement corrosion resistance.

Ni-W-P ternary coating was successfully deposited on AZ91D magnesium alloy by electroless plating with low energy consumption. The effect of Na2WO4 concentration on the microstructure, deposition rate, corrosion behavior, adhesion force, porosity test and micro-hardness of Ni-W-P ternary coatings were evaluated. Results reveal that when the concentration of Na2WO4 is 15 g/L in the plating solution, the coating with the average thickness of 17 μm is uniform and dense, and the content of phosphorus and tungsten reached 9.63 wt.% and 1.14 wt.% respectively, which presents amorphous structure. Meanwhile, when the concentration of Na2WO4 is 15 g/L, the amorphous Ni-W-P ternary coating has the best corrosion resistance, among which Ecorr is -0.326 V, Icorr is 0.003 A/cm2 in 3.5 wt.% NaCl solution. In addition, the mechanisms of corrosion resistance for the substrate and the coating were exploded.

Ni-Co-Al2O3-MoS2 composite coatings were prepared on the surface of LY12 aluminum alloys by electrophoresis-electrodeposition with different MoS2 concentrations. The microstructure, morphologies and composition of Ni-Co-Al2O3-MoS2 composites were characterized by X-ray diffractometer (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive spectroscope (EDS). The micro-indentation hardness as well as friction and tribological properties of the coatings were tested by micro-hardness tester and friction and wear tester separately. Results revealed that the composite coating fabricated at 1.0 g⋅L-1 MoS2 achieved dense structure, and the average thickness of the coating was 39.820 µm. The micro-indentation hardness of the composite coating was decreased from 578 HV to 465 HV with the increase of MoS2 concentration. Also, the composite coating synthesized at 1.0 g·L-1 MoS2 had the lowest friction coefficient and wear rate.

The rheological properties of cement-based materials can be used to guide its construction. In this paper, rheological characteristics of fresh cement mortar (FCM) were investigated. The rheological model and its parameters of the FCM under different hydration time, different water to cement ratio (w/c) and sand to cement ratio (s/c) were obtained by the rheological testing and model analyzer. The result indicated that rheological model of the FCM is transformed from Burgers model to Bingham model with the extension of hydration time. And the model transformed from Burgers model to five component model with the decrease of w/c and the increase of s/c. However, the superplasticizer has little effect on the rheological model of cement mortar. The plastic deformation of the fresh cement mortar increased gradually with the prolongation of the hydration time, and the plastic yield value increased gradually from 50Pa to 250Pa with the increase of s/c. The change rate of plasticity of mortar is reduced from 422Pa/h to 107Pa/h with the increase of superplasticizer’s dosage, which shows the addition of superplasticizer retards the hydration rate.

Ni and B co-doped diamond-like carbon (Ni/B-DLC) films were synthesized on the surface of AZ91D magnesium alloy by electrodeposition under mild environment. The formation mechanism of Ni/B-DLC films was discussed. The microstructure of the films was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results conveyed that the Ni-DLC and Ni/B-DLC films were hydrogenated amorphous carbon films. With the co-doping of Ni and B, the protruding mulberry-like structure of carbon-based films gave way to the compact and uniform granular structure. The intensity ratio (ID/IG) of D and G lines was decreased from 0.75 to 0.71. XRD patterns revealed that the doping of boron favored the sp3 hybridization of carbon atoms. Simultaneously, the infrared spectra demonstrated that hydrogen for Ni/B-DLC films was preferentially bonded with sp2 carbon atom. In addition, Ni/B-DLC films had excellent wear resistance, which was mainly attributed to the homogeneous and dense structure and considerable micro-indentation hardness.