Deposition and Characterization of Multilayer DLC/BN Films

In this article, the results obtained from a study on multilayer diamond-like carbon and boron nitride (DLC/BN) films are reported. The microstructure, atomic concentration, hardness and friction coefficient of the films were characterized using transmission electron microscopy, auger electron microscopy, nano-indentation measurements and ball-on-disk friction testing. The effects of bilayer thickness and substrate bias on film growth were investigated. All multilayer films showed alternate DLC and BN layers, except the 2- and 4-nm bilayer of multilayer DLC/BN films deposited without substrate bias. Although the layers were very thin, each layer was distinguishable. This was confirmed by the use of TEM imaging and AES measurements. The hardness values of all the multilayer films were lower than those measured for the monolayer DLC and BN films. However, the hardness can be altered with a change in the bilayer thickness. Furthermore, in the case of the films deposited with substrate bias, multilayer DLC/BN films showed an improvement in wear resistance compared to monolayer DLC and BN films. Thus, the deposition of multilayer DLC/BN films can be considered to be beneficial in prolonging the service life of the surface.

Improvement of Thermal Stability and Tribological Performance of Diamond-Like Carbon Composite Thin Films

Diamond-like carbon (DLC) is a metastable amorphous film that exhibits unique properties. However, many limitations exist regarding the use of DLC, for example, its tribological characteristics at high temperature, as well as its limited thermal stability. In this study, silicon/oxygen and silicon/nitrogen co-incorporated diamond-like carbon (Si-O-DLC and Si-N-DLC) films are studied, taking into account the thermal stability and tribological performance of these films compared with pure DLC. All the films were prepared on Si wafers, WC-Co materials, and aluminum foils using a plasma-based ion implantation (PBII) technique using acetylene (C2H2), tetramethylsilane (TMS, Si(CH3)4), oxygen (O2) and nitrogen (N2) as plasma sources. The structure of the films was characterized using Raman spectroscopy. The thermal stability of the films was measured using thermogravimetric and differential thermal analysis (TG-DTA). The friction coefficient of the films was assessed using ball-on-disk friction testing. The results indicate that Si-N-DLC films present better thermal stability due to the presence of Si-O networks in the films. The Si-N-DLC (23 at.%Si, 8 at.%N) film was affected using thermal annealing in an air atmosphere with increasing temperature until 500°C. The film can also resist thermal shock by cycling 10 times between the various temperatures and air atmosphere until 500°C. Further, Si-O-DLC and Si-N-DLC films exhibit excellent tribological performance, especially the Si-N-DLC (23 at.%Si, 8 at.%N) film, which exhibits excellent tribological performance at 500°C in an air atmosphere. It is concluded that Si-O-DLC and Si-N-DLC films improve upon the thermal stability and tribological performance of DLC.

Effects of Fluorine and Silicon Incorporation on Tribological Performance of Diamond-Like Carbon Films

Diamond-like carbon (DLC) is a metastable amorphous film that exhibits unique properties. However, a number of limitations exist regarding the use of DLC, for instance, its tribological characteristics. In this article, the fluorine and silicon incorporated diamond-like carbon (F-DLC and Si-DLC) films are studied, taking into account the tribological properties of these films compared with pure DLC. The structures of the films were characterized using Auger electron spectroscopy and Raman spectroscopy. The hardness and elastic modulus were evaluated by nanoindentation hardness testing. The friction behavior was assessed using ball-on-disk friction testing and optical microscopy. The results indicated that the deposited DLC films contained 0.6 - 2.1 at.% F and 26.7 - 38.4 at.% Si. A decrease in the hardness and elastic modulus was obtained as F increased in content, which was the opposite of the behavior observed in the Si-DLC films. This was due to the shifting in the G-peak position, which is related to the sp3 bonding fraction in the film. When measured in ambient air, the addition of Si into the DLC film strongly influenced the friction coefficient, whereas doping with F only slightly influenced the films, as evidenced by their wear scars. In addition, only a 26.7 at.% Si-DLC film showed a very low friction coefficient when measured in dry air. This was attributed to the formation of silicon-rich transfer layer on the ball surfaces. Therefore, the addition of Si with 26.7 at.% content to a DLC film can be considered beneficial for improving tribological performance.

Heat Resistant Properties of Some Elements-Incorporated Diamond-Like Carbon Films and Their Trial Applications for Micro End Mill Coatings

In this article, the results obtained from a study carried out on the some elements-incorporated diamond-like carbon (DLC) films are reported. All the films were deposited using plasma-based ion implantation (PBII) technique. The deposited films were annealed at 400℃, 650℃ and 900℃ in an air atmosphere for 1 hour. The effects of adding hydrogen, silicon/oxygen and silicon/nitrogen into the DLC film on chemical composition, friction coefficient and corrosion resistance were investigated. The films coated micro end mills performance was also assessed. The results indicate that all the films showed almost constant atomic contents of C, Si, O and N until annealing at 400℃. However, the films were completely destroyed at 650℃ with the increased Si and O contents, while the C content decreased. The incorporation of silicon/oxygen and silicon/nitrogen into the DLC exhibited lower values of friction coefficients than the hydrogenated DLC (DLC and H-DLC) before and after annealing at 400℃, whereas all the films presented the same values of friction coefficients after annealing at 650℃ due to the completely destroy of the films. Furthermore, the incorporation of silicon/nitrogen into the DLC also exhibited better corrosion resistance and unbroken micro end mills performance on their surfaces. Thus, the incorporation of silicon/nitrogen into the DLC film can be considered beneficial in improving the micro end mills performance.