From unidirectional to orthogonal grooves: orientation-controlled tribological mechanisms of TiN coatings

Laser surface texturing (LST) is widely employed to enhance the frictional stability and wear resistance of hard coatings; however, the role of groove orientation, particularly orientation combinations, remains controversial. Here, the tribological behavior of titanium nitride (TiN) coatings deposited on laser-pretextured stainless steel substrates is investigated using three representative groove configurations: parallel (PT), vertical (VT), and orthogonal (OT). Dry-sliding experiments combined with finite element stress analysis are performed to elucidate the coupled evolution of friction, surface degradation, and interfacial stress. The results demonstrate that PT exhibits pronounced frictional instability accompanied by coating deterioration, whereas VT maintains relatively stable friction but suffers the most severe material loss. In contrast, OT achieves the most stable frictional response and the lowest wear, with average coefficients of friction reduced by 36% and 29% and wear rates reduced by 62% and 76% compared with PT and VT, respectively. Wear mechanism analysis reveals that PT is dominated by debris saturation and longitudinal stress accumulation, VT by localized microcutting and edge wear, whereas OT effectively suppresses these failure modes through coordinated debris accommodation and stress redistribution. These findings provide a unified mechanistic explanation for the contrasting tribological behaviors of different groove orientations and identify OT texturing as an effective strategy for achieving stable and durable tribological performance under dry sliding conditions.