| Preparation of ceramic coating by electrical discharge coating (EDC) in liquid is novel metal surface modification method and there is little report on the research especially for the multi-components ceramic coating. The research was done with the common electrical discharge machine and the multi-components ceramic coating was prepared on the surface of45steel by electrical discharge coating in liquid. The temperature field of the coating was simulated by finite element numerical analog analysis method, and the effects of tool electrode, liquid medium and the discharge parameter on the morphology, element composition and phase composition of coating were researched. The hardness and tribological properties were detected.1. The temperature field of the electrodes in the process of the electrical discharge coating was simulated by the FEM ANSYS software. The proper heat source model and heat boundary condition were chosen, and then the heat conduction model of TiC ceramic coating on the surface of45steel prepared by EDC in liquid was established. The effect of pulse current parameters on the temperature field and surface morphology were studied. The results showed that:the maximum temperature of the tool electrode is much higher than the maximum temperature of the work piece, and the temperature decreases rapidly in the axial, while the radial temperature distribution is more uniform; the maximum temperature decreases slowly with the increase of peak current; with pulse current increases, the crater-like coating particles deposited on the workpiece is significantly increased.2.(Ti, Al) C ceramic coating was deposited on the45steel workpiece surface by EDC in liquid. The titanium and aluminum powder was compacted in the mold and then sintered in the vacuum furnace. The density, phase and the morphology of the tool electrode were studied. Multi-component ceramic coatings were deposited under different pulse discharge parameters, and the surface and cross section morphology, composition changes and phase composition were detected, moreover, coating hardness and tribological properties of coatings prepared under different parameters were measured. The results show that the density and relative density of the tool electrode increased with Al content, and when Al content is60%, the density reaches a critical value. The main phases also transform from Ti, Ti3Al, TiAl to Ti, TiAl TiAl3with the Al content. A droplet crater-like morphology presents on the coating surface and as the tool electrode Al content increases, the droplet size grow bigger whose thickness is about20μm. Results show Ti, Al, C, Fe exist in the coating and the main phase contains (Ti, A1)C and a small amount of Fe. The average hardness of the coating reaches up to1800HVo.2which is around five times of the substrate; the friction coefficient curves illustrated the friction coefficient of45steel is the highest and initial coefficient of the coating prepared under parameter of I(A)=8, Ton (μs)=20, Toff(μs)=:20and I(A)=12, Ton (μs)=80, Toff(μs)=150are the lowest and possess the best tribological performance which can withstand the longest time at the load of80N.3. Ti (C, N) ceramic coating was deposited on the45steel workpiece surface by EDC in ethanolamine liquid solution. The tool electrode was the Ti smelting electrode. Composition, phase composition, surface morphology structure of the coating were analyzed. The results show that:the coating contains the elements of Ti, C, N, Fe, the main phase of the coating is Ti (C0.3, No7). It shows an irregular and radial edge on the surface and sedimentary layers with a certain amount of microporous micro-cracks, the thickness is about20μm. TEM results shows that the coating formed equiaxed grains on the surface and the grain size is very uniform, the continuous bright SAED patterns show that equiaxed grains on the surface have the random orientation on the crystallography. Friction coefficient curve shows parameter2#(I=20A, Ton=3,Toff=3) lowest coefficient of friction and as time goes on, the friction coefficient increases slowest. After3.5min, the friction coefficient tends to0.4. Parameter1#(I=20A, Ton=8, Toff=8) and6#(I=30A, Ton=3, Toff=8)friction coefficient increase the fastest and the coating destructs instantly. |
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