Pulsed laser deposition of high-quality tribological coatings

摘要

Advanced materials are being designed and tested for use on ball bearings that have wide-ranging applications in almost any type of spacecraft. There has been considerable interest in 'hard' or wear-resistant coatings for protecting steel surfaces present in bearing components. Titanium carbide (TiC) has received serious consideration as a wear-resistant coating material that could be suitable for use in such applications. At present, the commercially available process for the deposition of TiC involves heating the steel substrates to fairly high temperatures. High-temperature coating deposition is not desirable for applications involving steel substrates as it results in a softening of the steels. This further necessitates post-deposition heat- treatments for re-hardening the steel and re-polishing the coating. This paper will describe the use of Pulsed Laser Deposition (PLD) to deposit high-quality thin films of TiC on bearing steels at room temperature. Such a process eliminates the problems associated with high temperature deposition, and the costs and complexities involved in the post-deposition heat treatment of steels. To develop an understanding of the deposition process, the plasma generated by laser ablation has been investigated using time-resolved emission spectroscopy. The PLD of TiC films on bearing steels, the material properties of these films, and the spectroscopy of the ablated plume will be discussed.