Research On Preparation And Process Of High Temperature Coating On C/C Composite Surface

C/C composite materials have the advantages of low density,high specific modulus,high specific strength,high toughness,ablation resistance and thermal shock resistance,low thermal expansion,thermal shock resistance,and have good mechanical properties at high temperatures.It is considered to be one of the most promising high-temperature materials.However,C/C composite materials have poor oxidation resistance,starting to oxidize at around 370°C under aerobic conditions,and start to burn above 480°C.Generally,the method of high temperature resistant oxidation coating or doping to change the matrix is used to improve the oxidation resistance of C/C composites.In this thesis,C/C composite material is used as the substrate,and the composite coating of Ni and ZrN is prepared by electroplating and magnetron sputtering respectively.Study the influence of different process parameters on the phase composition,micro morphology and mechanical properties of Ni coating and ZrN coating.The Ni-ZrN composite coating was tested and analyzed for high temperature oxidation resistance.The phase analysis and microscopic morphology study of the coating show that when preparing the Ni coating,the diffraction peak of nickel electroplating in the plating bath at about 55 ? is "sharp",indicating that the crystallization is better.Observation under a microscope electron microscope revealed that the coating is composed of spherical particles with almost no defects on the surface.When preparing the ZrN coating,when the nitrogen flow rate increases,the diffraction peak is(200)as the preferred orientation and tends to turn to the amorphous state,and the large particles on the coating surface are not dense.Coating hardness research shows that when preparing Ni coatings,increasing the temperature of the plating solution is beneficial to increase the hardness,but the hardness will decrease if the temperature increases.The maximum hardness of the plating solution is 284.1HV measured at a temperature of 45?.When preparing the ZrN coating,it was found that the hardness of the tested composite coating was increased by about 25% compared with the single Ni coating,and the maximum was358.3HV.Research on the wear resistance of the coating shows that the wear rate of the sample after electroplating the nickel layer is much lower than that of the C/C composite substrate itself,and the wear rate of the composite coating after magnetron sputtering ZrN is almost all less than that of a single coating.It is proved that the composite coating can effectively improve the wear resistance of C/C composites.Integrating the performance test of Ni coating and composite coating and the orthogonal experiment of magnetron sputtering ZrN coating design,the best parameters of the actual composite coating can be obtained.Nickel plating: voltage 1.70V;current0.10A;plating time 15min;plating solution temperature 50?;magnetron sputtering zirconium nitride: sputtering pressure 2Pa,sputtering power 160 W,nitrogen flow rate25 sccm,negative bias voltage 120 V,sputtering The temperature is 250°C.Two methods of thermal shock test and static oxidation test were used to test the oxidation resistance of the composite coating.After thermal shock test,the sample can withstand more than 35 thermal cycles at 800°C,and the coating begins to fail after 28 thermal cycles at 1000°C.There are coated samples at various temperatures.The thermal shock weight loss rate of the coated sample is much lower than that of the uncoated sample;the static oxidation test shows that the composite coating fails in high temperature and aerobic conditions,which can effectively protect the C/C composite material.The weight loss rate of the coated sample is higher than that of the uncoated sample.The layer sample is reduced by about 60%.