High-Temperature Tribological Performance of Al2O3/a-C:H:Si Coating in Ambient Air

Abstract

The study investigates thermal stability and high temperature tribological performance of a-C:H:Si diamond-like carbon (DLC) coating. A thin alumina layer was deposited on top of the a-C:H:Si coating to improve the tribological performance at high temperatures. The a-C:H:Si coating and alumina layer were prepared using plasma-activated chemical vapour deposition and atomic layer deposition, respectively. Raman and X-ray photoelectron spectroscopy were used to investigate the structures and chemical compositions of the specimens. The D and G Raman peaks due to sp2 bonding and the peaks corresponding to the trans-polyacetylene (t-Pa) and sp bonded chains were identified in the Raman spectra of the a-C:H:Si coating. Ball-on-disc sliding tests were carried out at room temperature and 400 °C using Si3N4 balls as counter bodies. The a-C:H:Si coating failed catastrophically in sliding tests at 400 °C; however, a repeatable and reproducible regime of sliding with a low coefficient of friction was observed for the Al2O3/a-C:H:Si coating at the same temperature. The presence of the alumina layer and high stress and temperature caused structural changes in the bulk a-C:H:Si and top layers located near the contact area, leading to the modification of the contact conditions, delivering of extra oxygen into the contact area, reduction of hydrogen effusion, and suppression of the atmospheric oxidation.

Tailoring Mechanical Properties of a-C:H:Cr Coatings

“…Also, an increase in FWHM of the G peak (from ≈112 to ≈130 cm −1 and ≈110 to ≈122 cm −1 for 0.66 Pa and 2.66 Pa, respectively), and D peak (from ≈334 to ≈339 cm −1 and ≈328 to ≈334 cm −1 for 0.66 Pa and 2.66 Pa, respectively), have been observed with the bias voltage application which is an indicator of more disordered amorphous coating. A decrease in the ratio of the D-band intensity to that of the G-band (I D /I G ) and the G-band position are both indicators of lower hydrogen content and a rising sp 3 content, respectively [29,30]. The chemical composition of the coatings as a function of depth has been obtained by XPS analysis and ERD analysis.…”

The Effectiveness of Diamond-like Carbon a-C:H:Si Coatings in Increasing the Cutting Capability of Radius End Mills When Machining Heat-Resistant Nickel Alloys

“…In recent years, great progress has been made by various research teams in the area of improving DLC coatings [50][51][52][53]. Various technological approaches are associated with alloying coatings by various metals and metalloids, in particular silicon, to stabilize the tribological properties of DLC coatings under high-temperature heating conditions.…”

High-Temperature Oxidation Resistance and Tribological Properties of Al2O3/ta-C Coating

“…According to Deng et al [19], the ta-C coating is easily peeled off at temperatures higher than 450 • C in ambient air. A more thorough discussion of the tribological behavior of the DLC and ta-C coatings at HT can be found in our recent publication [21].…”

“…An alternative approach to reduce the wear at extreme conditions includes the preparation of an adaptive top layer (for details see Refs. [21,22]). It was shown in our previous studies on nanocrystalline diamond (NCD) and a-C:H:Si coatings coated with the thin Al 2 O 3 layer that the alumina layer acts as an adaptive layer [21][22][23].…”

“…[21,22]). It was shown in our previous studies on nanocrystalline diamond (NCD) and a-C:H:Si coatings coated with the thin Al 2 O 3 layer that the alumina layer acts as an adaptive layer [21][22][23]. The increasing of wear scar width and therefore decreasing of contact pressure were observed in the sliding tests at room temperature (RT).…”