Experimental bending tests and numerical approach to determine the fracture mechanical properties of thin ceramic coatings deposited by magnetron sputtering

摘要

In this contribution, the fracture behaviour of a thin ceramic coating was investigated (Zirconia stabilized in its high temperature with Yttria was deposited by reactive magnetron sputtering, MS on high temperature Ni-based alloys substrate). A home-made bending apparatus was used to subject a thin small plate-like sample to a four-point bending test. An increasing bending moment was imposed in order to produce a set of crack patterns running right across the width of the sample bent. The bending apparatus is small enough to fit into the chamber of a scanning electron microscope (SEM) in order to measure the number and the crack positions along a selected portion of the sample length. The data was analysed under the assumption of a statistical Weibull distribution. A numerical computer simulation was performed to estimate the number of cracks, the cracks distribution, the fracture strength and the fracture toughness of the thin coating material. It was used an analytical model that assumes a stress relaxation, during cracking of the coating. It was observed that a selective choice of the Weibull distribution parameters has led to a good agreement between the experimental and the simulated data. (c) 2004 Elsevier B.V. All rights reserved.