Morphological Characterization And Wearability Analysis Of Aerosol Sealed Coatings

Medium and low temperature sealing coating is a protective coating widely used in the gap between the blades and the casing of aero engine compressors.It plays a role in reducing the gap,sealing the gas path,increasing the weight-to-weight ratio,and improving fuel efficiency.The most important property of the abradable seal coating is the abradability of the coating.The mechanical properties of the coating,especially the hardness,have a very important influence on the abradability of the coating.Since the coating has two different soft and hard phases,the morphology,distribution,and particle size ratio of each phase will have an important effect on the surface hardness of the coating.Therefore,the measured value of the surface hardness has a large jump and is difficult to accurately measure.Therefore,in order to explore the influence of coating hardness on the abrasion resistance of coatings,the concept of engineering hardness was introduced to characterize the friction and wear properties of coatings.Engineering hardness is the combined value of coating micro-morphology and two-phase micro hardness.For the evaluation of abrasion resistance of sealed coatings,high-speed scraping experiments were used to verify and evaluate.First of all,this paper analyzes and summarizes several typical sealing coating abrasion resistance evaluation methods and criteria,and then compares with the preliminary experimental results to determine the evaluation method and Criteria.Secondly,this paper starts with the surface micro-morphology,and introduces fractal method to characterize the shape,distribution and proportion of large and small particles of abradable phase of sealed coating,and uses box counting method to calculate relevant parameters.The simple fractal dimension can well characterize the rounding degree of the abradable phase profile of the coating,and the multi-fractal spectrum can well characterize the uniformity of the abradable phase distribution and the ratio of the number of large and small particles.The microhardness values of the coating matrix phase and the abradable phase were measured,and the two-phase mixing rule was used to combine the microscopic morphology of the coating and the microhardness values of the two phases of the coating to obtain an engineering hardness value that characterizes the comprehensive hardness of the coating.And divided into 5 grades from small to large according to the engineering hardness.Finally,the friction and wear coefficients of five types of sealed coatings were measured by a UMT-2 friction and wear tester.The high-speed scraping experiments were used to analyze the friction and wear mechanisms and abradability of different engineering hardness coatings under different scraping conditions.According to the actual working conditions of the sealed coating on aero engines,the types of high-speed scraping experiments are divided into two types,one is scraping at high speed and low invasion rate of blades,and the other is under low speed and high invasion rate of blades.Scraping.Comparative experiments of changing blade speed settings under these two types of scraping were conducted to analyze the scraping behavior response of coatings with different engineering hardness under different scraping conditions.In this paper,the relationship between the coating morphology and different spraying process parameters is analyzed through the characterization of the abradable phase shape,the distribution unevenness,and the size and number ratio of the sealed coating,and the relationship between the coating morphology and the coating mechanical properties is established.Correspondence between the friction and wear coefficient of AlSi-PHB sealing coating and engineering hardness;The friction and wear mechanism of different effective hardness coatings under different scraping conditions is analyzed,and the wearable performance criterion of the blade and coating wear quality ratio n is used.The combination of friction and wear mechanisms of the coatings is combined to obtain An AlSi-PHB seal with a class II engineering hardness seal coating is the best,that is,a polyphenyl ester content of 55% to 58%,a polyphenylene phase multifractal spectral width of 0.5909 to 0.6218,and a simple fractal dimension of 1.8511 to 1.8534.