Papers by Author: Ming Jiang Dai

Abstract: The combination of diamond-like carbon (DLC) coatings and fluid lubrication is an efficacious method to improve the performance and service life of the friction-pairs working under the severe conditions, but the synergistic effect of DLC coatings and lubricant additives have not been clearly unveiled. The synergistic effect of Cr-doped DLC coatings with different Cr content and the lubricant additives of ZDDP, MoDTC, and T307 on the wear of DLC-coated stainless steel sample was studied, and it was found that the wear resistance of DLC-coated stainless steel sample can be further improve by the combination of DLC coatings and fluid lubrication; doping DLC coatings with Cr at an optimum level is beneficial for the wear resistance of DLC-coated stainless steel sample lubricated by PAO, PAO+ZDDP or PAO + MoDTC, but DLC coatings with a moderate Cr content is harmful to the wear resistance of DLC-coated stainless steel sample lubricated by PAO+T307. The synergistic effect of T307 and undoped DLC coatings or Cr-doped DLC coatings with a Cr content of 23.3 % is the best, while the three studied lubricant additives are harmful for the wear resistance of DLC coatings with a Cr content of 2.4 %.

Abstract: Ti-doped DLC films were synthesized from C2H2 and Ti by ion beam deposition and magnetron sputtering, and the influence of Ti target current on the structures and the friction coefficients of Ti-doped DLC films were studied by SEM, AES, XPS, a ball-on-disk friction tester. The Ti content in Ti-doped DLC films is below 1at% when Ti target currents rise up to 3.5 A; but when Ti target current exceeds 3.5 A, Ti content in the films is obviously increased with increasing Ti target current. Ti-doped DLC films have a smooth dense surface with several particles dispersed in it and the surface morphology deposited with different Ti target currents is similar. With the augment of Ti target current, the ratio of sp3-C to sp2-C is almost a constant first, and then an obvious rise followed by an abrupt decrease is found; but only when Ti target current is above 5A, the ratio of TiC-C to sp2-C is obviously increased with Ti target current. The lowest friction coefficients are obtained for the Ti-doped DLC films with the highest ratio of sp3-C to sp2-C and a low ratio of TiC-C to sp2-C.

Abstract: W-doped DLC films were synthesized from ethyne and tungsten by ion beam deposition and magnetron sputtering, and the influence of W target current on the structures and the properties of W-doped DLC films were studied. There exist some defects smaller than 3micron in W-doped DLC films and the influence of W target current on the defects is unobvious. The W content in the films is tardily increased with W target current below 3.5A, and then acutely rises with W target current. When target current is below 3.5A, the ratio of sp3-C to sp2-C is first decreased and then increased with the rise of target current, and the ratio of WC-C to sp2-C is close to 0; but when the target is above 3.5A, the ratio of sp3-C to sp2-C is decreased and the ratio of WC-C to sp2-C is augmented with further increasing target current. The hardness and the modulus is first decreased with target current and the minimum value is reached for the W-doped DLC films deposited with a target current of 2.6A. The W-doped DLC films deposited with a target current of 2.6A exhibit the best film-substrate adhesion. The W-doped DLC films deposited with a low target current exhibit a friction coefficient while the wear resistance of the W-doped DLC films deposited with a medium target current of 2.6A is best.

Abstract: W-doped DLC films were synthesized from CH4 and W by ion beam deposition and magnetron sputtering, and the influence of W target current on the surface morphology and the mechanical properties of W-doped DLC films deposited were studied. The W-doped DLC films in the study have a smooth dense surface with several particles of about 2micron. The hardness, the modulus, and the film-substrate adhesion of the films are increased with the rise of W target current and the critical load of the scratch test for all the W-doped DLC films is above 70N. The friction coefficient of W-doped DLC films is increased with the increase of W target current while the lowest wear rate is obtained when W target current is 1A.