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Diamond-like carbon (DLC) films containing single copper (Cu), single nickel (Ni) and double nickel/copper interlayers were fabricated on LY-12 aluminum (Al) alloy by electrodeposition. The influence of different interlayers on the microstructure, microhardness, friction and wear properties and electrochemical behavior of the films was investigated. The morphological results show that the porosity of DLC films was reduced and the particles were refined after the introduction of a double interlayer. Raman and X-ray photoelectron spectroscopy results confirm that the amorphous characteristics of DLC films containing nickel and copper interlayers were enhanced, and the content of sp3 carbon in the films was increased. Besides, an optimal microhardness of 210.67 HV was achieved due to the high sp3 carbon content of the double nickel/copper–DLC film. Meanwhile, the nickel/copper–DLC film possessed excellent wear resistance, which benefits from the synergistic effect of the copper and nickel interlayer. Nickel as the supporting layer and copper as the lubricating layer alleviated the wear and friction of the film. Simultaneously, the deposition of a double interlayer increased the density of the film, which further prevented the invasion of corrosion ions, so the film had superior electrochemical properties.

Purpose This paper aims to research the effect of different concentrations for Nd(NO3)3 and Ce(NO3)3 on the microstructures and corrosion resistance of Ni-W-P composite coatings through electroless plating method. Design/methodology/approach Scanning electron microscope, attached energy dispersive spectroscopy system and X-ray diffraction were used in this work. Meanwhile, the immersion test and electrochemical tests were used to characterize the corrosion behavior of the coating. Findings The coatings prepared at 1.00 g·L−1 Nd(NO3)3 exhibit a dense structure and high phosphorus content (12.38 wt.%). In addition, compared to the addition of Ce(NO3)3, when Nd(NO3)3 was introduced at a concentration of 1.00 g·L−1, the minimum corrosion rate of the coating was 1.209 g·m−2·h−1, with a noble Ecorr (−0.29 V) and lower Icorr (8.29 × 10−4 A·cm−2). Originality/value The effects of rare earths on the deposition and corrosion resistance mechanisms of Ni-W-P composite coatings were explored, with the rare earth elements promoting the deposition of nickel and tungsten atoms. Simultaneously, the amorphization of the coating increases, which excellently enhances the corrosion resistance of the coating.

WC-12%Co-6%Cr coatings were deposited by high-velocity oxygen-fuel spraying technology (HVOF) on 42CrMo steel, and then, the sealing treatment was carried out by sol–gel aluminum phosphate inorganic sealing agent. The phases and porosity of the coatings before and after sealing were characterized by XRD and metallographic grayscale method, and high-temperature sliding wear tests were carried out at five different temperatures. The results showed that the coating/substrate bonding was mainly mechanical bonding with metallurgical bonding, and the high-temperature friction and wear mechanism of the coating was mainly contact fatigue and oxidation wear. The porosity of the coating was significantly reduced by aluminum phosphate sealing treatment, which was less than 2%, and the density was significantly improved. With the increase in wear temperature, the wear rate of the coatings increased, and the effect of phosphate sealing on reducing the wear loss was gradually weakened, and the highest service temperature was found near 450 °C.

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.

Combining a technology of a composite coating and a new development idea of a functionally gradient deposits, a kind of novel gradient nickel–tungsten–zirconium dioxide (Ni–W–ZrO2) composite coating was successfully prepared on LY12 alloy substrate by using concentration of sodium tungstate varying as 20 g/L, 50 g/L, 80 g/L, 120 g/L, 160 g/L, and 200 g/L in the bath. The results showed that the W content of as-deposited gradient Ni–W–ZrO2 composite coating was gradually increased to 50.50 wt% along the coating growth direction, its structure transitioned from amorphous to crystal line, and the tungsten nickel (Ni4W) phase was precipitated after heat treatment at 400 °C for 1 h. In addition, the wear and oxidation resistance, and anti-corrosion of gradient Ni–W–ZrO2 composite coating were generally enhanced with increase in heat treatment temperature. Moreover, the wear resistance, oxidation and corrosion resistance of gradient Ni–W–ZrO2 composite coating achieved optimal values after heat treatment at 400 °C for 1 h for the gradient structure and high W content.

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.

A kind of novel Ni–P gradient coating/stannate conversion film was deposited on AZ91D magnesium alloy (AZ91D alloy) by an integrative method involved stannate conversion and electroless plating. The results indicated that using sodium hypophosphite concentrations varied as 5, 10, 22, 46, and 60 g/L in the bath, the electroless Ni–P gradient coating with typical cell morphologies was successfully prepared, and the structures transited from crystalline → microcrystalline → amorphous were obtained as increasing P content from 3.31 to 12.58 wt%. Furthermore, the corrosion morphologies, polarization curves, and the electrochemical impedance spectroscopy result indicated that the corrosion resistance of AZ91D alloy substrate was significantly improved and the corrosion resistance of Ni–P gradient coating was superior than that of stannate conversion film, which might be attributed to the gradient structure and rising P content with unique function.

A kind of novel anti-wear and self-lubricating Ni-GO-CNTs composite coatings were deposited on the surface of AZ91D magnesium alloys substrates by an integrative method involved electrophoresis and electrodeposition with various CNTs (carbon nanotubes) concentration. The surface and cross-sectional morphologies of Ni-GO-CNTs composite coatings were studied by scanning electron microscope equipped with an energy dispersive spectroscope. The micro-indentation hardness as well as friction and tribological properties of Ni-GO-CNTs composite coatings were tested by micro-hardness tester, friction and wear tester separately. Results showed that the Ni-GO-CNTs composite coatings prepared successfully were strongly combined with the copper coating and the magnesium alloys substrates. The maximal micro-indentation hardness value of Ni-GO-CNTs composite coating was obtained with 0.04 g/L CNTs added. The wear resistance of Ni-GO-CNTs composite coating increased initially and then decreased with increasing the CNTs concentration. When the concentration of CNTs was 0.04 g/L, the friction coefficient and wear capacity of the composite coating exhibited the minimum value, which is mainly due to the cross-linking effect of CNTs and GO (graphene oxide) that enhanced the physicochemical properties of the CNTs and GO, indicating better mechanical properties of Ni-GO-CNTs coating.

Ni–Co–Al2O3 composite coatings were prepared by pulsed electrodeposition and electrophoresis–electrodeposition on aluminum alloy. The content of Al2O3 particles of the Ni–Co–Al2O3 composite coating prepared by electrophoresis–electrodeposition was significantly higher than the composite coating prepared by pulsed electrodeposition. The composite coating prepared by electrophoresis–electrodeposition exhibited a better anti-wear performance than that prepared by pulsed electrodeposition. The morphology, composition and microstructure of the composite coatings were determined by means of X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The hardness and friction properties of the samples were tested on the microhardness tester and the friction and wear loss tester respectively.

AZ91D magnesium alloy substrate was first pretreated in a phosphoric acid to obtain a phosphate coating, and then, the electroless ternary Ni-W-P coating was deposited using a sulfate nickel bath. The morphologies of the Ni-W-P coating were observed by using scanning electron microscope, the deposition rate of the coating was examined with the method of gravimetric analysis, and the phase analysis was identified by x-ray diffractometer. Electrochemical property was tested by means of an electrochemical analyzer. The results indicated that the addition of an optimum concentration of CeO2 (cerium oxide) particles could evidently improve the deposition rate and the stability of the plating bath. However, it acted as an inhibiting effect as the concentration of CeO2 particles exceeded to 8 mg/L in the sulfate nickel bath. The results also revealed that the morphology of Ni-W-P coating became more smooth, compact and uniform with the increase in the concentrations of CeO2 particles in the bath, but the corrosion resistance decreased due to the precipitation of crystal phases (Ni3P, Ni4W, etc.) after heat treatment.

Ni-Al2O3-MoS2 composite coatings were prepared on the surface of aluminum alloy substrates by an integrative method of electrophoresis and electrodeposition from the electrolytic solution with different MoS2 concentrations. The surface morphology and compositions of the coatings were studied by scanning electron microscopy equipped with an energy dispersive spectroscope. The microindentation hardness and tribological properties of the coatings were tested using a Vickers hardness tester and friction performance tester in dry sliding condition, respectively. Results showed that the cross-sections of the coatings exhibited smooth morphology and uniform distribution of the compositions. Al2O3 and MoS2 particles were uniformly dispersed in the Ni matrix. The coatings were sufficiently adhered on the aluminum alloy substrates. The addition of MoS2 particles can significantly improve the wear resistance of the coatings. When the MoS2 concentration is 1.0 g/L, the Ni-Al2O3-MoS2 coatings exhibit superior mechanical properties.

Ni-Co alloy and ZrO2 micron particles were codeposited on 45 carbon steel by electrodeposition. The composition and microstructure of the composite coating were characterized. The high temperature tribological properties were carried out by a pin-on-disk tribo-tester. Additionally, the oxidation resistance was evaluated via high temperature circulating oxidation test. The results indicated that the deposited composite coating showed dispersed ZrO2 particles and continuous Ni-Co matrix, and there were no obvious pores, cracks and other defects at the interface between the composite coating and the substrate. The embedded ZrO2 particles changed the friction mechanism from adhesive wear to abrasive wear, the wear loss rate and friction coefficient of Ni-Co-ZrO2 composite coating were lower in comparison with that of Ni-Co alloy coating and carbon steel substrate. In addition, the embedded ZrO2 particles exerted a reactive-phase effect on the growth of nickel oxide and cobalt oxide, and effectively reduced the oxidation rate of the substrate at high temperature. Therefore, the Ni-Co-ZrO2 composite coating presents better oxidation resistance, when compared with Ni-Co coating.

Carbon fibre reinforced Si3N4 (CF/Si3N4) biomimetic laminated ceramic composites were prepared through rolling, alternate stacking of two-dimensional carbon fibre cloth and Si3N4 green layers, burning out of organic components and hot-press sintering. The effects of the sintering process and sintering additives on the microstructure, fracture behavior and toughening mechanism of the composite were analysed. When sintered at 1850°C for 1.5 h with Al2O3, Y2O3 and MgO as sintering additives, a fully densified composite was obtained with homogeneous and moderate bonding interfaces between CF and the Si3N4 matrix, presenting improved flexural strength of 374.93 MPa and fracture toughness of 10.71 MPa m1/2, which were increased by 13.20% and 71.36% respectively, as compared with the monolithic Si3N4 ceramic. The primary toughening mechanism of the composite can be concluded as multiple crack deflection at the carbon fibre layers, fracture and pull-out of CF bundles and single CF within the carbon fibre layers.

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.

A kind of novel anti-wear Ni-TiC composite coatings was deposited successfully on 42CrMo steel by pulsed electrodeposition method with various TiC particles concentration. The effect of TiC concentration on morphologies and properties of Ni-TiC composite coatings were investigated and the optimum concentration of TiC particle was obtained. Results demonstrate that TiC particles were distributed uniformly in the Ni-based coatings and Ni-TiC composite coatings consisted of refined nickel nanocrystalline size. When the TiC particles concentration was 32 g/L, the highest volume percentage of TiC particles with 23.9 Vol.% and maximum micro-indentation hardness of the Ni-TiC composite coatings with 475 HV were achieved. Ni-TiC composite coatings show significant improvement in wear resistance in comparison with TiC free Ni-P coating.

Short carbon fibre (Cf) reinforced TiCN-based cermets (Cf/TiCN composites) were produced by powder metallurgy method with pressureless sintering technology. The phase evolution, microstructure and fracture morphology of Cf/TiCN composites were investigated. The results showed that TiC, TiN, WC, Cr3C2 and Mo phases disappeared gradually and diffused into core and rim phases by dissolution–reprecipitation process, finally formed new hard TiCN core phases and complex compound (Cr, W, Mo, Ti)(CN) rim phases, with the sintering temperature increasing. The added Cf did not change the ‘core–rim’ microstructure but improved the mechanical properties of TiCN-based cermets. The Cf/TiCN composite containing 3 wt-% Cf achieved the best comprehensive mechanical properties, with fracture toughness and bending strength increasing by about 14.4% and 30.8%, respectively, when compared with the composite without Cf. Toughening and strengthening mechanisms of Cf/TiCN composite were concluded as crack deflection and branch, ...

Ni–TiC composite coatings were prepared on substrate of aluminum alloy by pulse electrodeposition. The plating parameters for optimizing wear and corrosion resistance of Ni–TiC composite coatings were selected by orthogonal test, including the TiC particles concentration, current density, duty cycle, frequency and stirring rate. A three-layer back propagation (BP) artificial neural network with Lavenberg–Marquardt algorithm was established by MATLAB, which was used to train the network and predict orthogonal experimental data. Additionally, the best combination of parameters of the composite coatings were predicted and verified by experiments. The wear and corrosion resistance of Ni–TiC coatings were characterized and analyzed. The results indicated that the BP mode, which shows a relative error of approximately 3 %, could effectively predict the wear and corrosion resistance of Ni–TiC composite coatings. Ni–TiC composite coatings deposited by optimal synthetic condition showed dispersed TiC particles and continuous Ni matrix, as well as excellent wear and corrosion resistance.

The influence of heat treatment from 500 to 1100 °C on the 5 wt.% H2SO4 solution-induced corrosion resistance of high-velocity oxygen-fuel sprayed WC-17Co coatings on 42CrMo steel was investigated, by using x-ray diffractometer (XRD), scanning electron microscopy (SEM)-energy-dispersive spectrometer (EDS), and polarization curve methods. XRD analysis showed decrease in W2C phase intensity with recrystallization of amorphous Co and generation of new Co3W3C and Co6W6C phases with heat treatment. Porosity distribution did not follow a particular pattern; it initially increased and then decreased with increasing temperature. Corrosion resistance sequence of the as-sprayed and heat-treated coatings in 5 wt.% H2SO4 solution was C-5 > C-9 > C-A > C-7 > C-11. Furthermore, microstructure and phase structure of heat-treated coatings revealed the formation of different discontinuous plate-like oxide films on the surface of the heat-treated coatings which indicated the vital effect of binder structure on the corrosion resistance.

Y2O3-doped TiCN-based cermets were prepared by pressureless sintering with powders TiC, TiN, Ni, etc. as main starting materials. The influence of sintering processes and Y2O3 on properties of TiCN-based cermets were investigated. The phase composition of TiCN-based cermets almost had no change with Y2O3 addition. The fullly densified TiCN-based cermets were achieved by P-2 sitering process. The fracture surface showed lots of small dimples caused by hard phase particles pulling-off, and the left hard phase particles were attached to the arborous dendritic matrix. The Vickers hardness, fracture toughness and bending strength of TiCN-based cermets increased firstly and then decreased with the increment of Y2O3 content. When Y2O3 contents were both 0.8 wt.%, compared with the P-1 sintered samples, the Vickers hardness, fracture toughness and bending strength of the P-2 sintered samples reached 14.84 GPa, 8.66 MPa·m1/2 and 660.4 MPa, which were increased by 7.9%, 6.1% and 45.8%, respectively.

Ni–P gradient coatings, gradient Ni–P coatings with rare earth (RE) Yttrium (Y) (coating A) and non-gradient Ni–P coatings with RE Yttrium (coating B) were prepared separately on LY12 aluminium alloy by an electroless plating technique. The corrosion resistance of the three kinds of coatings in different corrosive environments were evaluated by corrosion weight loss rate and polarisation curve analysis. The Ni–P gradient coating had a thickness of about 40 μm, with phosphorus content gradually increasing from 6.27 wt-% in the innermost layer (crystalline structure) to 14.74 wt-% in the outermost layer (amorphous structure), thus protecting the substrate from corroding. Furthermore, the introduction of RE Yttrium (Y) into the Ni–P matrix can correspondingly improve the corrosion resistance of the coatings. Consequently, the corrosion resistance of the coatings in acidic and alkaline environments is characterised by coating A>coating B>Ni–P gradient coating, while in neutral environment is character...

Co-Ni alloy and ZrO2 submicron particles were successfully co-deposited on carbon steel substrate by direct current electrolytic deposition. The micromorphology, constituent, microhardness, corrosion and wear resistance of the composite coatings were tested, respectively. The results show that the embedded submicron ZrO2 particles are uniformly distributed in the entire Co-Ni matrix and the coating showed a good adhesion to the substrate. The hardness, friction coefficient, wear loss, and electrode voltage of Co-Ni alloy coating were 356 HV, 0.8, 1.901×10-2 mg/m, and-0.47 V, respectively, while those of Co-Ni-ZrO2 composite coating were 413 HV, 0.6, 1.174×10-2 mg/m, and-0.37 V, respectively. The data above suggested that Co-Ni-ZrO2 composite coating possesses higher microhardness, better wear and corrosion resistance.

Ni-P alloy and SiC micron particles were codeposited on Q235 steel by electroless plating. The composition, microstructure, micro-hardness, corrosion resistance and oxidation resistance of the composite coating were studied. The results revealed that the deposited composite coating shows dispersed SiC particles and continuous Ni-P matrix. When the content of SiC was 8g/L and the heat treatment temperature was 300°C, the corrosion potential and corrosion current of Ni-P-SiC coating were-0.292V, and 8.2×10-7 A/cm2, respectively, while those of Ni-P composite coating were-0.501V, and 4.2×10-5 A/cm2, respectively. Ni-P-SiC composite coating with high content of SiC exhibits better oxidation resistance than Ni-P coating.

The plating parameters for optimizing the wear and corrosion resistance of Ni-TiC composite coatings were selected by orthogonal test, mainly including the TiC particles concentration, current density, duty cycle, frequency and stirring rate. A three-layer BP (Back Propagation) neural network with Lavenberg-Marquardt algorithm was established by MATLAB, which was used to train the network and predicted orthogonal experimental data. In addition, the best parameters combination of the composite coating were predicted and verified by experiments. The results predicted through the proposed BP model are in good agreement with the experimental values, the relative error is small, and the maximum error is less than 3% and the coefficient of determination value is 0.9997.

Nickel matrix and Si3N4 micron particles were co-deposited on the aluminum alloy by pulse electro-deposition for high temperature performance. Meanwhile, the oxidation resistance was evaluated through the high temperature oxidation test. The phase structure, micrographs and components of the composite coatings were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) together with energy dispersive spectroscopy (EDS) respectively. The results indicated that Si3N4 particles were uniformly distributed across the coating and there were no pores and cracks or other defects at the coating/substrate interface. Ni-Si3N4 composite coatings are characterized by pyramidal micro-crystallite structure. The thickness of Ni-Si3N4 composite coatings were up to 80 μm for 2h. The results also revealed that the Ni-Si3N4 composite coatings presented better oxidation resistance than the pure Ni coating and aluminum alloy at high temperature. After oxidation at 673 K for 8h, the oxidation resistance of Ni-Si3N4 composite coatings presented the improved oxidation resistance behavior compared to pure Ni and the aluminum alloy, respectively.

Ni-Co-Al

The growth of microarc oxidation (MAO) coatings on aluminum substrates was controlled via changing solution temperature from 10 to 60 °C. The results show that an elevation of the temperature lowers the applied voltage and the coating thickness. The coating formed in low-temperature solution demonstrates large-sized pores and contains lots of elements only originating from solute such as P, W, and V. On the contrary, numerous small-sized pores disperse homogeneously on the coating synthesized in high-temperature solution. It is assumed that the variation of solution temperature affects the dissolving capacity of the alkaline solution and the adsorptive capacity of solute anions, thus dominating the growth behaviors of MAO coating.

Ti(C,N)-based cermets were prepared by pressureless sintering using micron-sized TiC and TiN powders as main starting materials and Ni and Co as metal binders. The fracture micrographs of Ti(C,N)-based cermets were observed by SEM. The effects of metal binder phase content on porosity and mechanical properties of Ti(C,N)-based cermets were investigated. The results show that when sintering at 1450 °C for 50min, typical core/rim microstructure is observed in the cermets, which is compact and distributed homogeneously, the density and relative density are 5.9 g/cm3 and 95.6%, respectively. Intergranular fracture is the main crack propagation mode, with a few of the transgranular fracture, and there are more dimples and tearing ridges in the fracture surface. Using the same sintering process, Ti(C,N)-based cermets with metal binder content of 10%Ni5%Co has a compact microstructure and fine grains, the metal binder phase is dispersed more evenly, the best vicker hardness, bending strength and fracture toughness of Ti(C,N)-based cermets are 15.8 GPa, 885.5MPa and 9.7 MPa·m1/2, respectively. However, Ti(C,N)-based cermets with Ni replaced of high Co content will generate some brittle intermetallic compound, its toughness is inferior to the metal binder phase, which reduces the strength and toughness of Ti(C,N)-based cermet materials.

Ni-B/Ni-B-B4C composite coatings on the substrate of medium-carbon steel (45#) were successfully fabricated by electroless plating in a low temperature bath. The corrosion resistance of Ni-B coating were examined by using electrochemical workstation. The results indicated that there are no pores and cracks and other defects at the interface between the substrate and composite coating. It was found that the corrosion resistance of Ni-B coating increased and then decreased with the addition of NaBH4 increasing, and the best addition in plating bath was about 0.9 g/L. While the corrosion resistance of Ni-B coating heat-treated at 400°C with NaBH4 addition 0.9 g/L was the worst.

Ni-P-multi-walled carbon nanotubes (Ni-P-MWNTs) composite coating was successfully co-deposited on 45 steel substrate by electroless plating. The microscopic morphology of Ni-P-MWNTs composite coating was observed by SEM. The influences of CNTs concentration in plating bath on the microstructure and corrosion resistance of the composite coating were investigated. The results indicated that the deposited composite coating shows dispersed CNTs and continuous Ni-P matrix, and there are no pores and cracks and other defects at the interface between the substrate and composite coating, and the thickness of the composite coating is about 50 μm. The Ni-P-MWNTs composite coating with 0.3g/L CNTs in bath displayed the best corrosion resistance, the corrosion potential of the composite coating is-0.372V.

Area-selectively liquid-phase sintering (AS-LPS) method was developed to control the coarsening of Si particles in Al/60vol.% Si composites with the help of sol-gel-derived interfacial modification, achieved by pre-coating discontinuous Al2O3 film on Si powders. The results show that due to the local presence of less than 1 μm-thick films, Si particles can approximately preserve their as-received size and morphology after being sintered at 950 °C. Whereas, for those prepared by use of the unmodified Si powders, Si phases evolve to several hundred-micron-sized flakes, being similar to the typical eutectic Si in Al-Si casting alloys. It is assumed that the Al2O3-film-coated areas at Al/Si interface control the dissolution of Si into Al liquid, while in uncoated areas Al matrix and Si particles bond together by LPS, thus realizing AS-LPS.

In this research, micro-hardness and wear resistance of two types of electroless coatings were investigated including Ni-P and Ni-P-B4C composite coatings. Dispersible B4C particles and electroless Ni-P alloy were codeposited on carbon steel by electroless plating and then heat treated at 200, 400 and 600 °C for 1 h, respectively. The cross-section morphology and microstructure of the composite coatings were characterized. Meanwhile, the micro-hardness and tribological behavior of composite coatings were evaluated. The results showed that the Ni-P-B4C composite coating presents better wear resistance in comparison with that of Ni-P coating. The Ni-P-B4C composite coating with heat treated at 400 °C exhibits high micro-hardness and good wear resistance, which the highest hardness is 1200 HV, the minimum wear weight loss is 0.12 mg and the lowest friction coefficient is 0.2054.