We have investigated the reactivity of metal-doped (Ti, WC) DLC coatings with the extreme-pressure (EP) dialkyl dithiophosphate additive. The results confirmed the chemical reactions between the EP additive and all the DLC coatings, as well as their oxidation during the tribological contacts. We measured an about 10-times higher chemical activity for the Ti-doped DLC compared to the WC-doped or non-doped DLC. The data also clearly show that even though small, some direct chemical activity between the W-DLC and dialkyl dithiophosphate is also possible without any iron catalytic effect.
COBISS.SI-ID: 11384347
We have calculated the contact temperatures for contact of diamond-like-carbon (DLC) coatings using two well-known models and compare them with results of tribological experiments and some state-of-the-art analyses of worn surfaces. The results showed that the actual surface temperatures are 100-130 °C higher than the test temperatures. A contact temperature of about 250-260 °C was found to be the required key activation criterion for chemical reactions between the dialkyl dithiophosphate extreme-pressure (EP) additive and the DLC coating.
COBISS.SI-ID: 11274267