Tribological behavior of PACVD TiN coatings in the temperature range up to 500 °C

Titanium nitride (TiN), is still the standard coating for cutting as well as forming applications. The aim of this study is to investigate the tribological behavior of low-friction plasma-assisted chemical vapor deposition (PACVD) TiN coatings with low chlorine content as well as the thermal stability of the low-friction effect. Dry sliding experiments at temperatures ranging from room temperature to 500 °C were conducted on PACVD TiN coatings, deposited onto high speed steel substrates. The coatings were worn against ball-bearing steel and Al2O3 balls using a ball-on-disc configuration. Characterization of the wear tracks was done by scanning electron microscopy, electron-probe microanalysis and an optical 3d profiling system. Extremely low-friction coefficients against ball-bearing steel and Al2O3 balls of 0.14–0.17 have been obtained at room temperature for coatings with chlorine contents between 3.2 and 3.7 at.%. The friction coefficient against Al2O3 increases to values of approximately 0.6–0.8 for temperatures above 70 °C. The lowest coating wear coefficient with 1.93×10−16 m2/N was obtained for Al2O3 balls at room temperature, whereas for temperatures exceeding 200 °C increased abrasion of the coating takes place, resulting in higher wear rates.