| The space science and technology of a country reflects its strategic will and contributes to its national security defense.It has broken through the limitations of the field of science and technology,and exerted far-reaching influence in areas such as politics,economy,military affairs,and even human life and development.Attitude control engine is the core propulsion device which provides power for missile weapons and spacecraft.It is widely used and highly required in the field of aerospace.As the key hot-end component of the attitude control engine,the anti-oxidation coating has a direct impact on the performance and reliability of the engine.The thermal performance test and service life prediction of the coating can provide important scientific basis for its manufacturing pro cess and material structure design.Therefore,they are of great scientific value to the development of aerospace technology.Since the heat transfer process of the anti-oxidation coatings is difficult to be analyzed accurately due to the different heating mechanisms and the time-varying temperature field characteristics,it is important to study the heat transfer mechanism of coating growth/volatilization in different heating mechanisms.Besides,the blind analysis of oxidation kinetics caused by the lack of theoretical basis in thermal performance analysis of coating is inevitable,so the methods for the analysis in different oxidation stages need to be explored.To tackle the problem that the thermal performance cannot be accurately tested due to the failure of online constant temperature heating in a wide temperature range and the aerobic/vacuum rapid thermal shock,the thermal performance test system was developed,which is the key focus of this study.In addition,since the traditional life prediction methods cannot give precise results due to the test interruption and oversimplification,new methods for the feasible and reliable service life prediction need to be explored.To solve the above mentioned,the following research work has been carried out in this study.The main research contents of this paper are as follows:(1)The study on the heat transfer model of the coating growth/volatilization in different heating mechanisms.The physical models of resistance heating,induction heating and radiation heating were deduced.The three-dimensional heat conduction analysis models of the anti-oxidation coating under different heating mechanisms were established.Those have revealed the non-uniform distribution of the surface heat of the coating growth/volatilization under different heating mechanisms.The heating rate of different heating mechanisms and the uniformity of the surface heat distribution under the condition of coating growth/volatilization were given by calculation.All the above has provided a theoretical basis for the design of the thermal performance test system.(2)The study on the methods for the thermal performance test of anti-oxidant coatings and the oxidation kinetics analysis.The measurement method of the thermal performance of antioxidant coatings based on mass method was studied.Moreover,a data processing method was established based on the proportional coefficient method,laiyite criterion,and weighted recursive average filtering.Further,the oxidation mechanism of coating was st udied,and the oxidation kinetics model of mass changes,oxidation rate and oxidation time of the antioxidant coating at different oxidation stages was established.Thanks to the oxidation kinetics model,the oxidation kinetics law of the coatings at the stages of oxidation,diffusion and shedding was revealed and the accurate analysis of the oxidation process of the coatings was achieved.(3)A thermal performance test system for the coatings used in the attitude control engine was developed.In the constant temperature test device,the vertical heating/cooling structure in different temperature ranges was designed.It makes it possible to do the online constant temperature heating/cooling in the temperature range from-180? to 2300?.In the aerobic/vacuum thermal shock test device,the rapid thermal shock heating structure was designed with the temperature rise rate up to 50?/s.The high vacuum test environment was also established.It makes it possible to engage in the rapid aerobic/vacuum thermal shock test at 500?2300?.The temperature control method of the target temperature value was studied to solve the problems of temperature overshoot and difficulty in accurate temperature control during the test.(4)The study on the failure mechanism and life prediction method of anti-oxidation coatings.By means of characterization and thermal performance test,the failure factors of coatings under different test conditions were studied.In addition,the life characteristic parameter theory and the single par ameter thermal cycle life prediction method were adopted.Based on the data of aerobic thermal shock life test,the factors leading to the thickness variation of the coating oxidation were introduced into the single parameter thermal cycle life prediction method.Thus,an aerobic thermal shock life prediction model was established,which took the average maximum thermal stress range value of the surface of the sample with different oxidation thickness of the anti-oxidation coating as a parameter variable.The results have shown that the method was feasible and the life prediction of anti-oxidation coatings was achieved.(5)Analysis on the experimental results and uncertainties of the thermal performance test system.Constant temperature and oxygen/vacuum t hermal shock tests were carried out with the thermal performance test system.The results show that the design of the system is correct and reasonable.The oxidation process of isothermal heating test was analyzed and the accuracy of the oxidation kinetics analysis was verified.The uncertainties of the test system were analyzed.The synthetic standard uncertainty for mass measurement was 0.19 mg.The synthetic uncertainty of the temperature measurement for the thermal shock test device is 1.65?,and that of the constant temperature test device is 3.19?. |
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