Abstract
This study investigates the effects of stored elastic energy gradient and compressive stress on the wear resistance of TiN coatings. TiN was deposited on Si and D2 steel substrates using DC unbalanced magnetron sputtering, where the in-depth energy gradient was tailored by stepwise tuning the working pressure ranging from 1.2 to 1.9 mTorr, including increasing (Pi), constant (Pc), and decreasing (Pd) pressure. The distributions of in-depth stress (σ
(γ)) of the coatings were determined using the average X-ray strain method with progressively increasing X-ray incident angles (γ). An energy-based calculation was proposed to convert the σ
(γ) distribution into a layer-resolved energy gradient (LEG). The chemical compositions and mechanical properties of the coatings maintained nearly constant, while the surface morphology and the LEG significantly varied with the tuning working pressure. Square pyramidal grains sporadically appeared on the TiN/D2 specimen deposited under condition Pc, while the conditions Pi and Pd were found to eliminate and promote the growth of pyramidal grains, respectively. The results showed substantially different LEG profiles among the specimens deposited under the three deposition conditions, primarily in the upper half of the coatings. Accordingly, wear tests on TiN/D2 specimens were conducted with two sliding distances (100 and 150 m). TiN coating deposited under condition Pd exhibited the highest adhesion strength (Lc2 ' 90 N) and the lowest wear rate (4.0 × 10
mm
N
m
) at the sliding distance of 100 m, where the square pyramidal grains partially enhanced the wear resistance. The wear rates varied between 100 and 150 m, which was attributed to the interplay between the LEG and compressive stress in the coatings. The results indicated that the surface morphology and LEG of the coating specimens could be tailored by stepwise tuning working pressure, thereby controlling the adhesion strength and wear resistance.