Growth and material properties of titanium carbide thin films for ball-bearing applications

Advanced materials are being designed and tested for high-stress and high-cycle bearings employed in spacecraft mechanisms. Hybrid bearings consisting of ceramic or ceramic-coated steel balls and steel raceways are being used to provide good fatigue performance and wear resistance in such applications. One of the coating materials that has received serious consideration in hybrid systems is titanium carbide (TiC). Until now the deposition of TiC has involved a process that requires heating the steel substrates to fairly high temperatures (similar to 1200 K). However, problems such as spallations and changes in composition have been observed with these TiC coatings when subjected to high stress. In light of these results, it has become critical to examine the issues involved in the deposition of TiC coatings for these applications, in particular, the deleterious effects of using a high temperature deposition process. Here we describe the use of pulsed laser deposition (PLD) to deposit high quality thin films of TiC on various bearing steels at room temperature. Such a process eliminates the problems associated with high temperature deposition, and the costs and complexities involved in the postdeposition heat treatment of steels. The material properties of room-temperature PLD-TiC films on 52100 and REX20 steels are discussed.