Hard ceramic coatings: an experimental study on a novel damping treatment

Abstract

This paper describes a novel damping treatment, namely hard ceramic coatings. These materials can be applied on almost any surface (internal or external) of a component. Their effect is the significant reduction of vibration levels and hence the extension of life expectancy of the component.The damping features of air-plasma-sprayed ceramic coatings (for example amplitude dependence, influence of initial amplitude) are discussed and the experimental procedure employed for testing and characterising such materials is also described. This test procedure is based around a custom-developed rig that allows one to measure the damping (internal friction) of specimens at controlled frequencies, strain amplitudes and, if required, various temperatures.A commonly used Thermal Barrier Coating, Yttria Stabilised Zirconia (8%), is used to demonstrate the above mentioned features. The damping effectiveness of this coating is then compared against two established damping treatments: polymer Free Layer Damping (FLD) and Constrained Layer Damping (CLD).The paper discusses the major issues in characterising ceramic damping coatings and their damping effectiveness when compared against the "traditional" approaches. Finally, the paper concludes with suggestions for further research.

Study of the amplitude-dependent mechanical behaviour of yttria-stabilised zirconia thermal barrier coatings

“…Through a numerical analysis the damping ratios 9 and the resonant frequencies of the coated beam are obtained from the decay. 4 These results are subsequently used in an inverse finite element (FE) routine to estimate the Young's modulus and loss factor of the ceramic material of the coating. 3 This is possible by implementing an exact FE model of the coated beam with a variable Young's modulus for the ceramic coating material.…”

“…In the past few years a mixed experimental-numerical procedure has been developed at the University of Sheffield for the characterisation of the non-linear properties of ceramic coatings. This procedure is built around a custom-built test-rig, the amplitude dependent damping (ADD) test rig, 4 and is capable of running tests over a wide range of strain amplitudes.…”

“…Recent studies have shown that ceramic coatings provide sufficient levels of damping to be a valid alternative to traditional damping treatments. [4][5][6] Moreover, these properties are virtually unaltered up to temperatures of 600 • C. Since the very first work that introduced the damping properties of ceramic coatings, 7 it has been shown that PS ceramic coatings possess an amplitude-dependent damping and stiffness behaviour. The level of damping and the resonance frequency of coated specimens vary with the vibration strain they undergo.…”

Enhancement in corrosion resistance and vibration damping performance in titanium by titanium nitride coating

“…When applied on the surface of components, hard coating can reduce resonant vibration levels by absorbing or dissipating energy and increasing the fatigue life of the components. The energy absorption/dissipation process is originated at internal defects, intergranular and substrate-coating interfaces, and dislocation motion [1,10,11]. Popular damping material, such as viscoelastic polymers, has temperature limitation and low stability in harsh working conditions [2].…”

“…Since the vibration dissipation mechanism does not depend only on the viscoelasticity, more thermally stable materials can be used as a suitable damper [12]. Some of the popular hard coating materials are 8 wt % Yttiria stabilized zirconia (YSZ) [11,13], polycrystalline alumina coating, NiCrAlY, FeCrAlY [8,14,15] and Magnesium aluminate spinel (MgO + Al 2 O 3 ) [3]. Torvik et al have compared the damping performance of magnetoelastic materials and plasma sprayed ceramic with a viscoelastic infiltrate [8].…”