Research Of Elastic Modulus And Damping Capacity Of Ceramic Hard Coating Based On Micro Scale

As an effective mean for improving the damping capacity and vibration fatigue resistance of the components,the hard coating has constitute a large percentage of industry engineering applications sunch as aircraft engine and gas turbine.Due to the large number of internal laminar interfaces and gaps,the typical hard coating microstructure,directly determine the mechanical and mechanical properties of the structure.In recent years,a large number of studies have been carried out on the effects of coating preparation on the coating structure and how to influence it,however less research on the microstructure of the coating and its mechanical properties and damping characteristics.Therefore,it is of great significance to study the relationship between the structure of hard coating and its macroscopic performance on the micro scale,which was in favor of a deeper understanding of the damping mechanism,and was important for active design and optimization of structure and properties of hard coatings..In this paper,a typical ceramic hard coating structure was studied.The relationship between the microstructure of the coating and its elastic modulus and damping characteristics were deeply investigated via the image processing method,experimental method and finite element method based on the microscopic structure.The main achievements are listed as following:(1)Two sets of 8YSZ ceramic hard coatings were prepared under the atmospheric plasma spraying method with different arc power.Compared to the microscopic appearance,the results show that the higher arc power can obtain the coating samples with relatively low porosity.(2)The storage modulus and loss factor of the two samples were tested under DMA methods at different temperatures.The results show that the storage modulus of the coating increases as the temperature decreased,the loss factor increases with the temperature increasing and then decreased.And at room temperature,the measured elastic modulus of lower porosity of coating sample a1 was 173.331 GPa,the loss factor was 0.003;the elastic modulus of high porosity coating sample a2 was 159.865 GPa,the loss factor was 0.0069.That is to say,the higher the porosity,the lower the storage modulus and the higher the loss factor.(3)The image processing method and the homogenization method was imported for the coating modeling and elastic modulus solving.Compared with the literature' test results and the DMA results of this article,the present method is convenient and efficient.(4)The simplified model of the coating,by choosing the appropriate microstructure parameters,was verified by compared the calculated elastic modulus with the experimental results.And then based on the simplified model,the relationship between the microstructure and the elastic modulus of the coating was studied.(5)The friction energy dissipation and loss factor of coating stucture were solved under a finite element model with micro crack to characterize the damping properties of the coating.The results show that the friction energy dissipation and the loss factor of the coating increase with the increase of the x direction loading,increase with the crack surface friction coefficient increase and then decreased,while the change in frequency is not obvious.