AVS 46th International Symposium
    Vacuum Metallurgy Division Wednesday Sessions
       Session VM-WeM

Invited Paper VM-WeM5
Protective Coatings for Extreme Environments

Wednesday, October 27, 1999, 9:40 am, Room 620

Session: Advanced Surface Treatments and Coatings
Presenter: H.W. Holleck, Forschungszentrum and Universität Karlsruhe, Germany
Correspondent: Click to Email
Physical Vapor Deposition (PVD) allows multifunctional protective coatings to be achieved for extreme and very complex loading situations. Among various thin-film concepts such as superhard coatings, gradient coatings, composite coatings, superlattice coatings, solid-solution coatings, metastable multifunctional coatings, nanoscale coatings, designed to improve the performance of protective coatings, the nanostructured multilayer films, the nanocrystalline composite films, and the metastable vapor-quenched compound films are able in particular to meet extreme requirements. Knowledge of specific design principles has developed over the past few years, thus adding a scientific design basis to what used to be empirical film development. Properties and functions simultaneously attainable include high levels of hardness, toughness, oxidation and corrosion resistance, abrasion and erosion resistance, as well as low friction and low wear in many applications. Multilayer coatings combining metallic hard materials e.g. TiC and TiN or TiAlN, metallic and covalent hard materials e.g. TiC and C or SiC, as well as combinations of hard and soft materials, e.g. TiN and MoS2 or C, will be discussed. Functional and structural contributions are responsible for the changes in properties produced by different numbers of single layers. Relations similar to those applying to multilayer coatings can be found for nanocrystalline films, with the grain size being the most important parameter besides phase composition. An almost unlimited source of new multifunctional coatings meeting extreme requirements are vapor-quenched multicomponent films combining materials of different hard material groups in a homogeneous film material optimized with respect to composition and structure. Examples to be discussed are TiC,TiN, TiB2, and CrN combined with compounds such as BN,B4C, SiC, and AlN. Thermodynamic and kinetic modeling of the coating system and the deposition process allows the constitution, properties and performance of these coatings to be tailored within broad limits.