Papers by Keyword: Composite Coating

Abstract: Duplex Ni-P/Ni-P-β-SiC coatings were prepared on 2605N double phase stainless steel substrate by electroless plating process. Experiments were carried out to compare and analyze the morphologies, composition and structure of Ni-P/Ni-P-β-SiC by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), XRD and electrochemical workstation, respectively. The results show that duplex Ni-P / Ni-P-β-SiC coating has good associativity between the coating and the substrate, β-SiC particles were uniformly distributed in the coatings, without pores, crack defects and so on. When β-SiC particle concentration is 15g/L, the microhardness reached maximum 623.285HV_0.20, In addition, when the β-SiC concentration is 15g/L, the corrosion reasistence is the best.

Abstract: This paper presents the thermophysical model of crystallization of the coating at the conditions of imperfect contact between the coating and sunstrate. The model takes into account the heat exchange of coating with the environment and with the substrate. The influence of thermal resistance of the interface and concentration of filler in the coating on the change of temperature during cooling is investigated.

Abstract: High temperature behaviour is important characteristic to be evaluated for internconnect materials in solid oxide fuel cell (SOFC) application. The present works concern in evaluating the morphological effect of composite coated SUS430, prospective material for SOFC application, on the high temperature behavior of the composite. Thermal spray method has been conducted as the major coating processes whereas thermal oxidation and sol gel coating is the addition coating method performed in the present works. Through variation of coating processes in the present works, different morphology of composite coated SUS430 alloy were obtained. Scanning electron microscope (SEM) characterizations have been performed in order to evaluate the morphological aspect of the coated samples before and after thermal oxidation process. In addition, X-ray diffraction characterization has been performed in order to identified the existing phase before and after thermal oxidation. From both characterization results, it was obtained that particle size of the composite layer influences the compactness and porous characteristic of the layer and in turn influences the oxidation characteristic of the layer during high temperature services.

Abstract: The purpose of the present study is to evaluate the effect of the electroless Ni-P/diamond/graphene composite coating on the structure and surface hardness of 2024-T6 aluminum alloy as well as their effect on the corrosion and wear resistance of the alloy in 3.5 % NaCl solution. The electroless Ni-P plating solution was prepared by adding different size diamond (6-12 μm and 0.2 μm) and nanographene into the electroless Ni-P plating solution to obtain Ni-P/diamond, Ni-P/graphene and Ni-P/daimond/graphene composite coatings for comparison. Experimental results indicated that the Ni-P/diamond, Ni-P/graphene and Ni-P/daimond/graphene composite coatings can be successfully electroless deposited on anodized 2024-T6 aluminum alloy. The anodically oxidized films, that formed on the aluminum alloy using phosphoric acid as the electrolyte, was porous with high density of pores, and thus could enhance the adhesion of the composite coatings. The Ni-P/daimond/graphene hybrid coating had a higher hardness as well as better corrosion and wear resistance of 2024-T6 alloy in 3.5 wt.% NaCl solution as compared with other composite coatings. When the combination of nanographene and smaller diamond particles added this beneficial effect was significantly raised, especially the composite coating was further vacuum annealed at 400 °C for 24 h to obtain a more smooth and defect-free coating structure.

Abstract: The aim of this paper is to study the effect of jatropha curcas biodiesel on the corrosion behavior of surface modified low alloy steel after modification by TIG torch surface melting technique. The coating layer was produced by preplacement of 1 mg/mm² TiC particulate into the surface of AISI 4340 steel and at heat input of 1344 J/mm using an electric arc generated from the tungsten electrode that melt the powder with substrate material to form a composite layer. The micrograph of the composite coated surface modified steel showed formation of TiC dendrites that densely populated at the of the melt pool which contributes to the high hardness value. The corrosion behavior of the composite coated steel was studied using tafel extrapolation method in biodiesel environment. The surface micrograph after corrosion test shows pitting corrosion holes as a dominant corrosion phenomenon for AISI 4340 steel. The tafel curve showed reduction of corrosion current density of the surface modified steel compared to the alloy street substrate.

Abstract: 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.

Abstract: 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.

Abstract: The multi-walled carbon nanotubes (MWCNTs) /polyvinyl alcohol (PVA) coating may have excellent biocompatibility and unique electrical properties. The effect of the dispersing agent on the electrochemical behaviors is very relevant,which has a great influence on the ionic conductivity of the composite material.We prepared four membrane electrodes of MWCNTs by using two dispersing processes of electrophoretic deposition (EPD). The scanning electron microscope (SEM) graphs of the MWCNTs/PVA composite were recorded In the NaOH solution, glucose is electrochemically oxidized on the acidified-MWCNTs/ PVA composite coating with high current density. The MWCNTs of the covalent dispersing methods treatment have a positive influence for the oxidation of glucose. The PVA can strengthen the dispersion effect of CTAB-MWCNTs for the EDP. The cooperative electrocatalytic property of MWCNTs-Pt toward glucose is not impaired by the association with the PVA binder.

Abstract: In this paper, TiC reinforced steel matrix surface composites were prepared by vacuum evaporative casting infiltration process and self-propagating high-temperature synthesis. The effect of original composition, binder types and original coating density on the hardness, wear resistance and microstructure of the coating were also studied. The results showed that the Ti and C content was 80% while added 3% PVA, by pressed at 200MPa pressure leading optimal coating quality. Meanwhile the average hardness was 62.5HRC and the wear rate was 22 % of high manganese steel.

Abstract: The electroless deposition technique was used to obtain Ni-P coatings with various phosphorus content. Machine vision method was applied as a tool for the analysis and interpretation of the data provided by electrochemical impedance spectroscopy (EIS) corrosion studies. The degree of corrosion of the coating surface could be determined by this method. The combination of both methods allows a more complete evaluation of the protective properties of the obtained coatings.