Nanostructured Composite Films on Engineering Substrates: Towards Functionally Graded Materials

Novel materials whose microstructure can be engineered to contain features in the nanometre scale represent a new class of engineering materials. These “nanostructured” materials can exhibit a range of technologically interesting properties including enhanced hardness, yield strength, toughness, and tribological performance compared with their conventional micrometre scale (or larger) counterparts. This project aims to develop superhard TiN-CrN nanocomposites with functionally-graded (Cr/CrTi/CrTiN) interlayers on engineering substrates (steel, cemented carbide, etc.) fabricated by close-field unbalanced magnetron sputtering and ion plating (CFUBMSIP). The main objectives are to establish the relationships between hardness/plasticity, gradual transition structure, grain size, stress, adhesion, and wear, and to understand the origin of a unique material system with excellent strength, toughness, and adhesion properties. The functionally graded (Cr/CrTi/CrTiN) interlayer is expected to have a gradual transition in bonding from metallic (Cr/CrTi) near the interface to predominantly covalent (CrTiN) near the surface, providing a combination of high toughness and high surface hardness as well as overcoming adhesion problems associated with nanocomposite hard coatings on metallic substrates. The outcome will provide both basic and practical knowledge of how these functionally graded superhard nanocomposites can be synthesized and directly used for a range of industrial and engineering applications.