Research On Preparation And Thermal Insulation Performance Of Thermal Protective Coating On The Surface Of Polymer Matrix Composites

The comprehensive performance of advanced polymer matrix composite is comparable to that of metal alloy,which can not only meet the requirements of mechanical properties,but also reduce the structure quality and improve the thrust-to-weight ratio when applied in the field of aerospace.Thermal barrier coating(TBCs)is an integral part of high performance engine due to its excellent thermal insulation and oxidation resistance.Therefore,this paper has carried out research on the preparation technology of protective coating for resin matrix composites,and used explosive spraying technology to prepare YSZ(X)ceramic protective coating with high binding strength and good resistance to high temperature air erosion on carbon fiber reinforced polyimide resin matrix composites.Through the design of low melting point metal as the underlying layer,guarantee the coating with composites interface better wetting spreading,the purposes of coating combined with high intensity,Ni Co Cr Al Y layer for the middle layer have the effect of stress buffering,containing ablative phase of YSZ for ablation resistant surface layer of three layer gradient composite system,to the preparation of the coating with low bonding strength,good thermal matching,and excellent advantages of ablation resistance.The research results show that:The simulation analysis of temperature field and stress field shows that the 0.4mm thick YSZ(X)coating can completely protect the substrate from thermal damage.However,considering the matching of the coating stress distribution,it is necessary to reduce the coating thickness.After sandblasting pretreatment,the bonding strength of the coating can reach up to 13.72 MPa,which is 195.1% higher than the original matrix bonding strength of4.66 MPa.The average bonding strength of the coating obtained by adopting the method of preheating on the front and slow cooling on the back is 12.23 MPa.Al metal is the most excellent as the bottom coating.Compared with Cu and Zn powders,Al powder particles have a spherical or elliptical morphology,with good particle dispersibility and excellent thermal stability.The Al coating is prepared on the surface of the composite material.The surface is dense,without peeling or cracks,the cross-sectional structure is relatively dense,and the interface is well combined,and there is no burn-out and interface cracks.Oxidation ablation exists in the cross-sectional structure of the Cu bottom layer,which causes serious thermal damage to the substrate.Compared with the Cu coating,the surface roughness of the Al coating and the Zn coating is lower,but the bonding strength between Al and the substrate is the highest,reaching 8.63 MPa,followed by Zn,and the Cu bonding strength is only 1.35 MPa.4# powder is selected as the base layer of the anti-ablation thermal barrier ceramics.The composition ratio is more suitable.The particles have good sphericity,dense and smooth,and the particle size distribution is between 30?m and 45?m.The thermal stability is good.The bulk density and fluidity meet the spray requirements.Combined with sandblasting pretreatment and front preheating plus back pre-cooling pretreatment,the composite coating prepared with Al as the bottom layer has a bonding strength of up to 16.60 MPa.Compared with the coatings with different surface layer thicknesses,Al-0.1mm+Ni Co Cr Al-0.1mm+YSZ(X)-0.3mm thickness coatings have excellent interlayer thermal matching performance and interface bonding performance with the composite material.During the preparation of the coating,there is no thermal damage to the substrate surface,the cross-sectional structure of the coating is uniform,the interface between the layers is tightly bonded.The anti-ablation time of 800? high-temperature impact is 328 s,a large number of holes and even collapse appear in the surface layer,the pores of the metal layer are reduced,and the structure becomes denser.After ablation,the bonding strength of the coating is reduced by 63.07% compared with that before ablation.It has good heat absorption capacity and volume stability during the high temperature experiment from 500?to 800?.Its thermal conductivity is close to that of conventional pure YSZ,but the average The density of about 3.355 g/cm3 is about 28.4% lower than that of the conventional YSZ,indicating that when the same thermal insulation effect is obtained,the coating prepared in this study is lighter in quality and has more development prospects for aeroengines.