2022 journal article
Shear activation of ZDDP reaction films in the presence and absence of nanodiamonds
APPLIED SURFACE SCIENCE ADVANCES, 7.
We explore the impact of shear stress and nanodiamond (ND) additives on the formation temperatures of thermal- and tribo- reaction films of steel samples immersed in basestock oils containing zinc dialkyl dithio-phosphate (ZDDP) additives. The measurements were performed in-situ using a quartz crystal microbalance (QCM) immersed in oil, oil plus ZDDP, and oil plus ZDDP-ND blends over the temperature range 25 200 °C. ZDDP reaction film formation temperatures were observed to decrease with contact stress and be similar in value to ZDDP-ND blends. ND were observed to be embedded in the reaction films, consistent with prior observations for Tricresyl phosphate (TCP) ND blends, and also consistent with the presence of both primary and secondary reaction products in the films. In addition, the ZDDP+ND reaction tribofilms were observed to be thicker, rougher and more adhesive than those formed with only ZDDP.