Preparation And Solid Particle Erosion Of SiC Coating On Low Density C/C Composites For Elevated Temperature Industry

Low density carbon/carbon composite has large number of inside pores, which has been used in metal heat treatment furnaces, single crystal furnace and polysilicon purification furnaces on the basis of high temperature insulation properties. Industrial devices typically untilize inert gas in cooling process, solid particles entrained in the gas become high speed particles flows, which result in material removal of thermal insulation material.To extend life span of low density C/C composite under extreme environments such as high temperature oxidation and solid particle erosion, high speed particles flows that impact surface directly should be stopped. The most immediate protective measure is preparing coating on low density carbon/carbon composite,which improves erosion resistance at the expense of coating.In this thesis,SiC coating on low density C/C composite was produced via silicon evaporation in view of poor erosion resistance, however, successful silicon carbide layer calls for a graphite coating and carbon based coating given on the substrate surface by means of a slurry coating technology.Influence of technological parameters on phase composition and microstructure of coating and erosion of low density C/C composite and surface coatings have been studied.The conclusions were presented by summarization of the experimental results as follow:(1) Carbon paper completely covers substrate,but surface of coating appears cracks, peeling and more severe delamination after deposition of silicon carbide. Carbon cloth has square micropores in the overlap of carbon fiber bundles and large size cracks parallel to axis of carbon fiber, but after deposition of silicon carbide, dyke type SiC coating perpendicular to the direction of crack expansion is formed on the surface of carbon fiber bundles.(2) Surface of low density C/C composite can be gradually into continuous and dense SiC coating by coating method which combines slurry coating technology and silicon evaporation. Along with time increases, thickness, density and microhardness of SiC coating increase. Only SiC exists on coating surface at1550℃with evaporation time of3h.(3) Density and surface evenness of SiC coating can increase gradually with low surface roughness of graphite coating by reducing particle size of graphite powder,silicon block as silicon source and argon as protective gas.(4) With the increase of gas pressure and erosion angle, erosion rate of low density C/C composite increases. Along with content of resin increases, solid particle erosion rate first increases and then decreases. Surface of substrate suffering solid particles erosion at the angle of60°,75°,90°, presents carbon fiber bundles.(5) As mass of solid particle erodent increases, erosion rate of carbon paper, carbon cloth and graphite coating before and after deposition of SiC coating decreases.SiC coated carbon cloth has a minimum of erosion rate and optimal erosion resistance. Surface of carbon paper after deposition of SiC coating by solid particle erosion exists pits and raised lip pieces.(6) SiC coated on graphite coating exhibits good solid particle erosion resistance with optimal experimental parameters for evaporation temperature:1550℃, evaporation time:3h.