TEM investigation of TiAlN/CrN multilayer coatings prepared by magnetron sputtering

Multilayer coatings TiAlN/CrN were deposited by reactive magnetron sputtering. Thickness of the individual layers varied from 2 nm to 25 nm while the total thickness of the coating was ∼ 5 μm. Coatings in cross-section were investigated using conventional, scanning and high-resolution transmission electron microscopy (TEM). Conventional TEM studies revealed a columnar microstructure. Chemical analysis of individual layers was preformed by high-angle annular dark-field scanning TEM (HAADF-STEM). The layers were well separated and no substantial intermixing was observed. High resolution TEM and electron diffraction studies showed that TiAlN and CrN layers are crystalline with B1 NaCl-type crystal structure. Coherent interfaces between TiAlN/CrN were observed, which can be attributed to a small mismatch between lattice parameters. In some areas between steel substrate (bcc-Fe) and the coating epitaxial relationship {001}Fe||{001}coating and <100>Fe||<110>coating was observed. In different areas of the coating TiAlN layers appeared to be less crystalline than CrN.