Using ta-CNx coatings deposited by the IBA-FAD (Ion Beam Assisted Filtered Arc Deposition) method, we conducted friction tests. The test results showed that the friction coefficient in dry friction of refrigerant environment was about 0.02 and the friction coefficient in mixed environment of refrigerant and refrigerating oil was 0.03 or less. The ta-CNx coatings expressed low friction coefficients about one-third or less of the friction coefficients of current DLC coatings (Diamond Like Carbon Coatings), which are generally about 0.1. Compared with the DLC coatings of other companies (which have been used for automobile engines) and no coating, which exhibits friction coefficients of 0.1 to 0.15, the ta-CNx coatings we developed showed significantly lower friction coefficients. Furthermore, in the environment of engine oil, under the condition where an additive agent was additionally mixed with the oil, the ta-CNx coating showed a low friction coefficient of 0.04. We observed the sliding faces after friction tests and analyzed them with reflectance spectroscopy. As a result, we found that there was tribo-film formed on the friction surface and clarified the low friction mechanism of ta-CNx coatings. In addition, as one example, we applied the developed ta-CNx coatings to the sliding parts of a compressor of an air conditioner and confirmed that the efficiency was improved by about 1%.
