Investigation of elemental distributions in TiAlN-ZrN multi-layers using analytical transmission electron microscopy

This microstructural characterisation is described of PVD multilayer coatings. Coatings of TiAlN-ZrN, approximately 3 mu m in thickness were grown on to stainless steel substrates using a combined steered cathodic are evaporation and unbalanced magnetron sputtering technique. The crystallography and the multilayer periodicities were investigated using X-ray diffraction. Electron-transparent cross-section samples were examined using a conventional transmission electron microscope interfaced with an imaging filter, and with a field emission gun scanning transmission microscope interfaced with an energy dispersive X-ray analyser and a parallel electron energy-loss spectrometer. Quantitative measurements of composition were acquired across individual layers of nominal 13.2 nm spacing using X-ray analysis, but not from layers with periodicity 2.6 nm. However, qualitative elemental distributions from layers of periodicity 2.6 nm were easily resolved using energy-filtered images. The energy-loss spectroscopy also revealed differences in the near-edge fine structure of the nitrogen edge between the two TiAlN and ZrN. It was not possible to clarify the extent of intermixing of the metallic elements between layers.