Narrow Results

Micro-arc oxidation technique (MAO) treatment produces a layer of alumina film on the surface of the aluminum alloy. A hard and uniform tetrahedral amorphous carbon film (diamond-like carbon, DLC) was deposited on the top of the alumina layer of the 2024 aluminum alloy by a pulsed filtered catholic vacuum arc (FCVA) deposition system with a metal vapor vacuum arc (MEVVA) source. The morphology and tribological properties of the duplex DLC/Al₂O₃ coating were investigated by a scanning electron microscope (SEM) and a ball-on-disk sliding tester. These results suggested that the duplex DLC/Al₂O₃ coating had good adhesion and a low friction coefficient, which improved significantly the wear resistance of aluminum alloys.

This study is focused on the tribological properties of micro- and nano-crystalline diamond (MCD and NCD), non-hydrogenated and hydrogenated diamond-like carbon (DLC and DLC-H) and nitrogen-based (CrN, TiN and TiAlN) coatings sliding against the super alloy Inconel 718, in terms of the maximal and average coefficients of frictions (COFs), the worn morphologies and the specific wear rates, by the rotating ball-on-plate configuration under dry condition. The results show that the nitrogen-based films show comparable COFs and wear rates with the WC–Co substrates. The DLC and DLC-H show lower COFs compared with the nitrogen-based films. Furthermore, their wear resistance is limited due to their low thickness compared with MCD and NCD, which have the same elemental composition. The DLC-H coating exhibits much lower wear rate compared with the DLC coating, which may be derived from the passivation of dangling bonds by the linking of H to C atoms. The MCD and NCD films show the lowest average COFs and mild wear after tribotests, due to their high hardness and low adhesive strength between pure diamond and the super alloy.

Among all the tested films, the NCD film-based tribopair presents the lowest maximal and average COFs, tiny wear debris particles, mild wear of ball and plate without scratching grooves, indicating that the NCD film may be suitable to be deposited on cutting tools for super alloy machining.

Tungsten incorporated diamond like carbon nanocomposite films were deposited onto Si substrate by using target biased ion beam assisted deposition. The effect of W target bias voltage on the chemical bonding, structure, surface morphology and mechanical properties of DLC films were investigated by means of XPS, Raman spectroscopy, AFM and Nanoindentation. It was found that the content of W in the films increased from 6 at.% to 13.7 at.% due to the increase in target bias voltage from -300 V to -700 V. XPS analysis revealed that most of the tungsten starts to react with carbon to form WC nanoparticles. Raman analysis shows that with the increase of W fraction in the DLC matrix, the intensity ratio I_D/I_G increases and the G band shifts to higher wavenumber. Thus it proves that the incorporation of tungsten leads to increase in sp² hybridized carbon content, and hence decrease in the hardness of W-DLC films compared to that of the pure DLC films. The result of AFM indicates that the surface roughness of the DLC gets modified with the incorporation of tungsten.