Research On Cylinder Bore Coating Using Plasma Spraying Technology

The wear failure of automotive engine cylinder was increasingly widespread attentionby people. This article analyzes the wear failure principle of the engine cylinder wall andsummarize the requirements for the performance of the engine cylinder innersurface.Based on this we identified the materials applicable to the preparation of thecylinder wall coating and produced four materials FeCrBSi, Ni60, Ni60-WC,Ni60-WC-Mo coating on Q235Steel through flame remelting after plasma spraying. Thisarticle analyzed the performance improvement after several coating through remelting.This paper studied the phase composition of the coating using scanning electronmicroscopy and X-ray diffraction,and made the text to the bonding strength, hardness,porosity and friction performance.The experimental results and analysis show:The organizationsof plasma sprayed coatings show the layered superimposed structureof the flat particles which contain cracks and holes. The sprayed layer structure is relativelyloose and internal microhardness uneven,this lead to the hardness decreases at loose tissue.The binding force between unmelted tungsten carbide and the surrounding matrix metal isnot strong,this lead to unmelted tungsten carbide come off easily under conditions of highstress abrasion.The hard phase of Ni60and Ni60coating primarily of chromium boride andcarbide. The Ni60-WC and Ni60-WC-Mo coating increased the hard phase WC and Mo2C.WC added significantly increase the hardness of the coating. The binding between thecoating and the substrate to the mechanical coupling.The cracks and pores in coating disappeared and the organizational structure is denseand the hard phase uniformly distributed in the remelting coating. The unmelted WCparticles spread fully around with the metal element diffusion and no hard phasesheddingfrom the base body when when frictioning in the remelting coating of Ni-WC.Inremelting process WC decomposition occurs, the generated W2C hardness is extremelyhigh. The addition of Mo will improve the bonding strength of the nickel-based tungstencarbide, to reduce the coefficient of friction of the coating.The combination which between the layer and the substrate is metallurgical bond is very strong.The hardness of coatingwhich remelting was increasedand within the coating uniform hardness distribution, andthe hardness distribution uniform within the coating. The microhardness of Ni60-WC-Mocoating had the biggest increasing,which increased by about1.8times, which is about1.4times Ni60coating and2times FeCrBSi coating under the same conditions. The wearresistance of Ni60-WC-Mo coating after remelting haver an increase of nearly three timesthan the original coating, which is about2.5times Ni60coating and4times FeCrBSicoating under the same conditions.