Diamond-like carbon films produced by pulse-biased DC glow discharge

Diamond-like carbon films have unique properties. They typically are more dense, harder and more resistant to chemical attack than any other solid hydrocarbon or carbonaceous polymer. Their low coefficient of friction and high wear resistance make them ideal candidates for wear resistive coatings on a variety of substrate materials. In this study, the deposition conditions for preparing diamond-like carbon films by the pulse-biased DC glow discharge were investigated and the microstructure and properties of the films were characterized.; The properties of the carbon films varied substantially, with the substrate material being a major factor. The films on Si and 440C stainless steel were hard and adhered to the substrate strongly. Films on pure Ni and Incoloy alloy 908 were sooty and peeled off easily. The chemical affinity of the substrate material appeared to be a major factor, possibly affecting the nucleation process and bond strength.; Raman spectroscopy and transmission electron microscopy illustrated that films deposited on a Si substrates, using a CH{dollar}sb4{dollar} plasma, were quasiamorphous and were composed of sp{dollar}sp3{dollar} and sp{dollar}sp2{dollar} bonds. Small clusters of sp{dollar}sp2{dollar} bonded carbon were formed. The interface of the DLC film and Si substrate consisted of a 300 A thick Si-C layer and a 300 A thick amorphous Si layer. The formation of these interface layers was explained in terms of ion implantation, diffusion and hydrogen enhanced amorphization. It is believed that the Si-C layer provided a strong chemical bond between the film and the Si substrate, resulting in high adhesion strength.; Nanoindentations were performed to measure the mechanical properties of the films. In addition, pin-on-disk and fretting wear tests were carried out for tribological study. The coefficient of friction of the DLC films was relative low compared to other hard coatings.; The failure mode obtained in the scratch test appeared to depend on the bond strength between the film and the substrate materials. However, the mechanical properties of both the film and substrate were also important. The film on Incoloy alloy 908 buckled and spalled, indicating that the film had poor adherence. The film on SS440C exhibited conformal cracking, which is typical a well bonded film on a ductile substrate. For films on Si, cracking initiated in the Si substrate, indicating that both film strength and the bond strength were higher than that of the Si.; Substantial structural changes of the DLC film occurred in the annealing temperature range of 400{dollar}spcirc{dollar}C to 600{dollar}spcirc{dollar}C. The direction of the change suggested a removal of bond-angle disorder and a growth in the number or size of crystallites. The crystallites were identified as threefold coordinate graphite.; Two half fraction factorial designs (2{dollar}sp{lcub}3-1{rcub}{dollar}) were set up to optimize the production processing of DLC films by the pulse-biased DC glow discharge. Two pressures were used: 15 mTorr and 30 mTorr. Three factors; bias voltage, pulse width and repetition rate, were chosen as main variables. The range of parameters used were selected to insure a stable and uniformly distributed plasma. The affect of these factors on deposition rate and properties, such as wear, friction, hardness and adhesion, were statistically analyzed.