A universal expression for interfacial indentation toughness of a ceramic coating on metallic substrate

Based on FEM calculations, a simple polynomial expression for surface strains of cone indented elastic–plastic solid was obtained using regression method, which facilitated an engineering solution for interfacial toughness of thin ceramic coatings on metallic substrates using just a standard Rockwell hardness test. Testification was made on a TiSiCN coating of steel substrate with a 50 nm thickness Ti interlayer to improve adhesion, and a reasonable value of the interfacial toughness of 205 J/m2 was gained.