Characterisation of TiN and TiAlN Thin Films Deposited on Ground Surfaces Using Focused Ion Beam Milling

TiN and TiAlN/TiN PVD coatings deposited onto as-ground surfaces have been characterised via direct cross-sectional imaging and transmission electron microscopy with the aid of a focused ion beam system. Cross-sections showed that the coatings exhibit consistent coverage, even in sheltered areas such as at the base of grooves resulting from prior grinding. A columnar grain structure was observed in all coatings. A number of defects were observed such as seams and voids resulting from coating onto the as-ground surface and macroparticles which were shown to be deposited during the metal ion etching stage. Cross-sections through nanoindents revealed that the coatings deform by through-thickness shear cracking. The combination of the excellent coverage provided by PVD and the deformation mechanisms, which are related to the microstructure, contribute to the excellent performance of these coatings that has lead to their widespread application.