Mechanical Parameters Identification Of Hard Coating Material And Its Mechanism Of Vibration Suppression

Hard coatings are usually deposited on substrate by means of Plasma Spraying, Physical Vapor Deposition. Hard coating and substrate constitute a composite structure, which is called coating-substrate composite structure. Mechanical properties of the composite structure are distinct from the single material or bulk material. For its small scale and elastic difference compared with the substrate, the identification results are inevitably influenced by the existence of substrate. Moreover, mechanical properties of hard coating often exhibit anisotropic. All the above factors bring about the difficulties of accurate identification. So, traditional experimental methods can not take these factors into consideration.In this paper, methods for identifying isotropic mechanical parameters considering substrate effect and transversely isotropic mechanical parameters of hard coating are proposed. Based on the identification results, finite element models are established to analyze the vibration characteristics of coating-substrate composite structure, which verify and confirm the reasonable material parameters applicable to vibration analysis. Furthermore, studies of vibration responses are conducted to examine the effectiveness of suppressing vibration for NiCrAlY coating. The details are following:(1) Focusing on the influence of substrate effect, the relationship between maximum indentation load, loading curve exponent and mechanical parameters, depth of indentation are established by finite element analysis. Combined with nanoindentation experiment, isotropic mechanical parameters are obtained.(2) Based on anisotropic elastic constitutive equations, NiCrAlY coating is simplified as transversely isotropic elastic body. Dimensionless equations between maximum indentation load, loading curve exponent and mechanical parameters of coating, depth of indentation are established by finite element analysis. Combined with nanoindentation experiment, transversely isotropic mechanical parameters are obtained.(3) Finite element model of coating-substrate composite structure are established considering the anisotropy of NiCrAlY, based on which, natural frequencies and vibration responses are calculated. Natural frequencies, modal damping ratios and resonant responses of Titanium thin plate deposited with NiCrAlY is measured. Furthermore, the result of both finite element analysis and measurement are compared, which verifies the correctness of mechanical parameters and the reliability of estimating resonant response.On the basis of proposing evaluation index of the damping effect, cantilever Titanium thin plate coated. with NiCrAlY is taken as example. Finite element method is adopted to calculate the above index, whose results reveal the good effect.The studies in this paper are significant to more accurately identify mechanical parameters, more accurately establish dynamic model, better evaluate the damping effectiveness of hard coating. Moreover, they lay the foundation for further optimization design of hard coating damping.