Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 50: Topical Session Modern Atom Probe Tomography IV - Thin Films and Structural Materials
MM 50.3: Vortrag
Donnerstag, 29. März 2012, 12:15–12:30, H 0107
Spinodal decomposition in TiAlN/CrN multilayer hardcoatings studied by atom probe tomography — •Ivan Povstugar1, Pyuck-Pa Choi1, Jae-Pyoung Ahn2, and Dierk Raabe1 — 1Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany — 2Korea Institute of Science and Technology, Seoul, Korea
Nanoscale nitride multilayers are good candidates for protective coatings for cutting tools and machine parts owing to excellent mechanical properties and corrosion resistance. However, they possess only a limited thermal stability at operational temperatures. To understand its origin, chemical information at an atomic scale is essentially required. We exploit atom probe tomography to study the thermal evolution of Ti(0.75)Al(0.25)N/CrN multilayers prepared by the sputter deposition.
TiAlN/CrN coating shows well-resolved layered structure with single layer thickness of 4.5 nm. The multilayers are stable up to 600°C when short-range diffusion at layer interfaces begins. At 700°C TiAlN layers undergo interface-directed spinodal decomposition. As a result, each TiAlN layer evolves into a sandwich-like structure consisting of a Ti-rich sublayer confined by two Al-rich ones. With the increase of time or temperature of thermal treatment, the interface-directed mechanism passes into common isotropic spinodal decomposition accompanied by intermixing between TiAlN and CrN layers in a close-to-surface region of the coating. Conversely, Al-rich layers remain clearly distinguishable in the deep region of the coating. The difference is ascribed to the non-uniform release of residual internal stresses during heat treatment.