Transmission electron microscopy of TiN and TiAlN thin films using specimens prepared by focused ion beam milling

The microstructures of a series of TiN and TiAlN wear resistant coatings on steel substrates are characterized using cross-sectional transmission electron microscopy. TiN coatings were deposited using both low-voltage electron beam evaporation and cathodic arc techniques, and a dual-layer TiN-TiAlN coating was prepared using cathodic are deposition. All of the coatings consisted of columnar grains separated by high-angle grain boundaries. In all specimens, the substrate/coating interface was sharp and no Ti interlayer or modification of the substrate was observed. The TiN/TiAlN dual-layer coating contained a layered interfacial region where both the Ti and TiAl sources were operating concurrently. The TiAlN regions consisted of extremely fine sub-layers similar to2 nm thick, which are thought to result from the threefold planetary rotation of the specimen in the deposition chamber. The columnar grains grew epitaxially through the entire TiN/TiAlN interfacial region. TEM specimens were prepared using the focused ion beam, which allowed large, uniformly thin areas to be prepared with relative ease. (C) 2003 Elsevier B.V. All rights reserved.