Deformation mechanisms operating during nanoindentation of TiN coatings on steel substrates

The deformation mechanisms operating during nanoindentation of TiN coatings on steel substrates were investigated using FIB cross-sectioning and imaging, as well as cross-sectional transmission electron microscopy of the indented region. Two coatings were investigated: a relatively thick (3.7 μm) coating deposited using a low voltage electron beam system, and a thinner (0.7 μm) coating deposited using a cathodic arc process. Load displacement data from nanoindentation displayed clear pop-ins as the load increased. Cracks were observed at the boundaries between the columnar grains, and steps were observed at the coating/substrate interface. A comparison of the load displacement data and the microscopic observations indicated that deformation occurs primarily by shear sliding along the columnar grain boundaries.