Pulsed Laser Deposition of Carbide Coatings for Rolling and Sliding Contact Applications.

摘要

In this research program several new concepts were investigated for improving the mechanical and tribological properties of coatings intended for applications subject to repeated rolling and sliding contacts. The investigation focused on four primary areas: (1) alloying carbides to enhance coating hardness, (2) depositing composite carbide-silver coatings for reduced friction in vacuum environments, (3) evaluating carbide-metal nacreous structures for improving coating toughness, and (4) chemical vapor deposition (CVD) methods for nanostructured composite carbide coatings. Results show that, in carbide coatings, additions of silicon can provide a useful and practical route towards improving coating hardness. This is due to the disordering effect of silicon when present in transition metal carbides. Investigation of composite carbide-silver coatings demonstrated their potential as low-friction coatings in vacuum environments. In these coatings, phase separation between carbide and silver allows the silver to act as a solid lubricant, while the carbide matrix improves wear resistance over silver alone. In the third research area, the authors evaluated whether increasing film toughness by using a metal layer in TiC-based films could enhance the wear resistance of such films. Results show that the use of thin (<10 mm) interlayers of Chromium can significantly improve wear resistance compared to monolithic TiC. These results were obtained with a newly developed reciprocating nano-scratch test method that allows testing of a coating independent of its adhesion to the substrate. Research on CVD of TiC- based coatings evaluated three areas of thermal CVD. Finally, plasma studies were performed to explore the reactor species present during the production of hard films in a parallel plate plasma reactor. Appendix includes a report from the Systran, Inc. subcontractors and 9 of the authors' publications in peer- reviewed journals.