プラズマCVD法により作製したSi-CNxHy膜の油中摩擦特性

抄録

Amorphous Carbon Nitride (a-CNx) coating is an attractive material that satisfies both relatively high hardness and ultra-low friction coefficient. We have tried to obtain a-CNx by using plasma-enhanced chemical vapor deposition (PECVD), which is more suitable for 3-dimensional coating than typical physical vapor deposition methods. However, considering the application of a-CNx coatings for real machine parts, ultra-low friction property is expected to express under oil lubrication. Thus in this work, the friction characteristic under oil lubricated of Si-containing a-CNxHy films deposited by PECVD was evaluated especially by analyzing the relation between the Raman spectrum, which is a proper index of carbon structure, and the friction coefficient of the films. In particular, the relation between friction coefficient and I_D/I_G ratio from Raman spectroscopic analysis of Si-containing a-CNxHy films was focused on. The friction coefficient decreased with the increasing of I_D/I_G ratio in the range of 0.63-0.78, and the minimum low friction coefficient of 0.055 was shown for the I_D/I_G ratio of 0.78. However, even for a film with the I_D/I_G ratio of 0.32, similar low friction coefficient of 0.051 was shown. Moreover, for a film with the I_D/I_G ratio of 0.34, which is almost unchanged from 0.32, the increased friction coefficient of 0.105 was shown. In these films, the amount of hydrogen in Si-containing a-CNxHy film increased from 33% to 37%, which is considered to mainly cause the increased of friction from 0.051 to 0.105. Two more exceptions were seen for some films where the friction characteristic is not correlated with I_D/I_G ratio, but may be affected by maximum height roughness (Rz) and C=N combination. When maximum height roughness (Rz) was in the range of 203 nm-414 nm, transfer layer formed on counter material, and it showed lowest friction coefficient of 0.02. In addition, the friction coefficient was linearly decreased with the increase of C=N bond amount; the friction coefficient of 0.027 was achieved for the I_C=N/I_G ratio of 0.44.