| Diamond-like carbon (DLC) films have wide application in many fields because of its high hardness, chemical stability and well tribological properties. W doped in DLC films can effectively improve the hardness wear resistances, improve the tribological performance. The W content was controlled by the sputtering current of tungsten target, were fabricated by ion beam deposition and magnetron sputtering. The correlation between W content, microstructure and mechanical properties of Diamond-like Carbon (DLC) films, the influence of W content and friction conditions on the friction coefficients and the wear rates of W-DLC films were discussed. The results as followed were shown:(1) There exist some particles and pits with a dimension of hundreds nm in the W-DLC films fabricated by ion beam deposition + magnetron sputtering. W content in the films is slowly increased with the rise of the sputtering current first, and then a obvious rise of W content with the aguement of sputtering current appears when the sputtering current excess 3.5A.With increase of W content, sp3-C content in the films with a low W content was obviously decreased, while the influence of W content on sp3-C content in the films is unobvious when W content is higher than 3.08at%. When W content reached to the level above 10.73at%, there exist WC in the films, and the WC content increased with W content.(2) With the increase of W content, the hardness and the elastic modulus of the films are gradually decreased first, and then they are increased after a lowest hardness and elastic modulus are reached for the W-DLC with a W content of 3.08 at%. The adhesion between DLC film and their substrates is best for the films with a W content of 3.08at%. The fracture toughness can be improved by the introduction of W into DLC films at an optimum level.(3) Under the dry sliding conditions, the friction coefficients of the DLC films with a W content below 10.73at%are slowly increased with the increase of normal load, and then kept at a steady value. The friction coefficients of DLC films whose W content is above 24.09at% are low at a high load. The lowest wear rates of all DLC films except W-DLC with a W content of 27.66 at% are found at a load of 1.96N; while the DLC films whose W contents are 27.66 at% exhibit a high wear loss with the rise of load. The influence of sliding rate on the friction coefficient of pure DLC films or the films whose W contents are 27.66 at% is unobvious; but when W contents in the films is in the range of 1.66~24.09at%, the low friction coefficients are obtained at a low sliding rate. For undoped DLC films and the films with a W content below 24.09 at%, the sliding rate has an unobvious influence on the wear rates, but the wear of DLC films with a W content of 27.66 at% are more rapidly worn with a rise of the sliding rate.(4) Under the PAO lubricated condition, the friction coefficients of the films are decreased with W contend; when the W content is below 10.73 at%, the content of W had less obviously influence on the wear rate; but the wear rates are markedly increased with a rise of W content above 10.73 at%. Under the PAO+MoDTC lubricated conditions, the friction coefficients are slightly affected by the W content increase. While the W content is below 24.09 at%, the wear rates of DLC films are decreased in the beginning, and then become higher with a rise of W content. Under the PAO+ZDDP lubricated conditions, the friction coefficients are slowly decreased with the increase of W content. The doping of W element can remarkably reduce the wear rate, but the influence of doping level is unobvious. Under the PAO+T307 lubricated conditions, the DLC films with W content of 3.08 at% or 24.09 at% exhibit a lowest friction coefficient, while the highest wear rates are found for the films with a W content of 1.66 at%.
|
PDF Full Text Request