| Summary: | <p>The indentation response of a series of filtered cathodic arc-deposited TiN, TiCN, CrN and ZrN coatings on M2 tool steel substrates was studied. Indentation tests were performed using Vickers microhardness tester and the Nanoindenter II™, and examined in secondary and backscattered electrons under the SEM, allowing crack systems developed under the indenter to be characterised in terms of spacing and length. Work-of-indentation arguments were used to consider the effect of cracking and interfacial debonding on the system hardness. In the present paper, the experimentally measured system hardness variation with relative indentation depth is described using newly proposed empirical formulae. The system response is being described using an overall toughness parameter, which incorporates the influence of coating fracture, interfacial delamination and limited coating plasticity.</p>
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