Research Of Damping Performance Of Multilayer Hard Coatings Considering Interlayer Dissipation

Due to high damping and anti vibration fatigue ability,hard coatings are widely used in key components of mechanical equipment such as aeroengine and gas turbine.The high damping of hard coatings mainly comes from a large number of micro defects,including interfacial cracks,internal cracks and micro pores.These micro defects have a decisive impact on the damping performance of hard coatings.In recent years,the research on damping properties of multi-layer hard coating composites mainly focuses on the macro application,while the research on internal microstructure parameters and damping properties is less,and the interlayer dissipation at the coating interface is not considered in the research process.Therefore,it has important engineering value and practical significance to study the relationship between the microstructure parameters of the multilayer hard coating and its damping performance on the basis of considering the effect of interlayer dissipation.In this study,the damping performance of the three-layer hard coatings is studied.Based on the three-layer coatings scanning electron microscope map to extract its pore and crack characteristics by image processing,the ABAQUS two-dimensional finite element model considering inter-layer dissipation effect is established.After studying the impact of microstructure parameters on the energy consumption and loss factors of three-layer hard coatings,and the method of finite element modeling and vibration characteristics were used to explore the vibration damping effect on the structure of the three-layer hard coat layer in the structure of the cantilever beam.The main research contents are as follows:(1)Three-layer hard coatings of Al₂O₃-Ni Cr Al Y-Zr O₂ were prepared on TC4 titanium plate by atmospheric plasma spraying.The microstructure of the coatings were observed by scanning electron microscope.The results show that the micro defects of the coatings are mainly composed of a large number of irregular pores and cracks,and there are obvious strip-shaped pores at the junction of different hard coatings.The energy dissipation of the three layers of hard coatings mainly comes from the interface crack and the internal crack of the coating.For the interface crack,the friction energy consumption of the cracks between the layers can be increased by properly increasing the elastic modulus difference between the two layers.(2)Based on the three-layer hard coatings SEM image,the pore and crack characteristics are extracted using Python,and imported into ABAQUS to establish a three-layer coatings two-dimensional model containing pores and cracks.The seam and cohesive units are used to simulate the cracks respectively.The loss factor of the three-layer coating under different stress loading is calculated.Comparing the calculation results with the test results of DMA,the calculation results are different from the test results due to the different loading stress,but they are in the same order of magnitude,which verifies the effectiveness of the above two methods in simulating crack energy consumption and calculating loss factor for multilayer hard coatings.(3)A simplified model of a three-layer coatings with a total thickness of 0.2mm was established according to the verified simplified method.Based on the above simplified model,the influence of the matching of microstructure parameters and elastic modulus on frictional energy dissipation and loss factor is studied,and the orthogonal test is designed with comprehensive consideration of multiple influencing factors.The results show that when the elastic modulus of the intermediate coating is small,the loss factor of the three-layer coating is large;the overall frictional energy consumption and the dissipation factor vary with the porosity and cracks of the intermediate coating The increase of density shows an upward trend;for the three-layer structure,the microstructure parameters of the middle hard coating have the greatest influence on the damping performance,and the crack density is the most critical factor affecting the damping performance.(4)The vibration characteristics of the three-layer coated cantilever beam and the uncoated cantilever beam and the Ni Cr Al Y coated cantilever beam were compared through the methods of finite element modeling and experimental testing.The finite element calculation results are in good agreement with the experimental test results.,verified the accuracy of the finite element modeling method.Moreover The damping properties of the two three-layer hard coating structures are compared by test.The results show that,compared with uncoated cantilever beams and Ni Cr Al Y coated cantilever beams,the natural frequency of the three-layer coating cantilever beam shifts,the modal damping ratio increases,and the amplitude response decreases significantly.For the three-layer coatings structure,the elastic modulus of the intermediate coating is small,and the overall damping performance is better,and the reliability of the simulation calculation results is verified.