  This paper studies the behaviour of a thin titanium nitride (TiN) coating
(1.5 um thick) on a tool steel substrate material under dynamic and cyclic
impacts through an approach combining experimental testing and computational
modelling. Dynamic impact testing was used to investigate the load-dependent
dynamic hardness and assess the energy-dissipation capabilities of the coating
system. In cyclic impact tests, the materials experienced permanent plastic
deformation in each cycle, ultimately leading to coating failure. Chemical
analysis identified an interlayer between the coating and the substrate, while
cross-sectional analysis revealed the extent of coating damage due to cycling
and impact load. A three-dimensional map was constructed, connecting the
acceleration load, sensed depth, and cycles to the coating failure, and an
empirical equation used to characterize the relationship between the depth and
cycles to failure. The computational model examined the traction component
distribution during loading and unloading, with a focus on normal and shear
tractions. These findings suggested the potential significance of normal
traction in the interfacial fatigue failure due to impact.
