Mechanical Property Data for Coated Systems-The Prospects for Measuring “Coating Only” Properties using Nanoindentation

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Abstract
One of the critical aspects of assessing the properties of coated systems is the prospect of being able to measure the properties of the coating in isolation of the substrate. This has led to an increase in the use of continuously-recording indentation techniques (or nanoindentation techniques) for assessing the mechanical properties of coated systems since they can be used to measure the materials response to contact deformation at a scale relevant to the coating thickness. This paper presents the results of a new method for analysing the nanoindentation loading curves for coated systems. The analysis of the loading curve uses the relationship P = Kmδ2 which describes the indenter displacement, δ, in terms of the applied load P. For each material, Km can be predicted from its modulus E and hardness H. One result is that if either of E or H is known, then the other may be calculated from the experimental loading curve. Further, the method has the potential to differentiate between the responses of the coating only, the coating and substrate in combination, and that dominated by the substrate once the load has become sufficient for cracking of the coating such that it no longer plays a significant role in supporting the applied load. In many cases, careful analysis of the loading curves allows the displacement ranges associated with these regimes to be identified. This is shown to be a powerful experimental tool for the interpretation of the mechanical properties of coated systems.