Our highly industrialized society is always in search of ways to reduce or control friction and wear of materials. Diamond coatings can provide an efficient solution for these problems. The focus of this research work is to study the potential of diamond coatings to improve the tribological properties of steel components. Although chemical vapour deposition (CVD) of diamond is well researched and well established on various non-diamond substrates, deposition on ferrous materials is difficult to obtain and not yet up to the stage of commercial realization. One of the main challenges associated is that iron comes under the group VIII transition metals and due to their partially filled 3d orbital, Fe atoms are highly reactive towards carbon. On the other hand, carbon also has a high coefficient of diffusion in the iron matrix. As a result, the incubation time to reach the critical carbon concentration is very long for steel substrates. Another major drawback is the thermal expansion coefficient mismatch between steel and diamond, which results in high thermal stresses upon cooling, leading to poor adhesion. Using various interlayer and surface pretreatment techniques, we have overcome the above mentioned problems and successfully obtained diamond coatings on steel substrates by hot filament chemical vapour deposition (HFCVD) technique. Tribological characterization of the diamond coated steel substrates was performed under small amplitude oscillatory motions, known as fretting. In this talk, an overview of the diamond CVD mechanism, challenges, interlayer systems and the fretting wear behaviour of the diamond coatings will be presented.
