Efficient friction and wear reduction of Al-Si alloy via tribofilms generated from synergistic interaction of ZDDP and chemically functionalized h-BN additives

Abstract

Zinc dialkyldithiophosphate (ZDDP) and molybdenum dithiocarbamate (MoDTC) are conventional lubricant additives for reducing friction and wear of metallic components. However, their efficacy for lightweight aluminum (Al)-based alloys is limited due to the wear of soft Al matrix regions. The present work reports significant improvement in the tribological properties of Al-Si alloys (ADC12) under liquid lubricants containing a combination of ZDDP and hexagonal boron nitride (h-BN) nanosheets. In situ monitoring of tribofilm growth, friction, and wear was carried out using atomic force microscopy (AFM)-based measurements. At high temperature (110 °C), experiments were carried out at the Al matrix and Si phase of ADC12 alloy under the lubricant containing ZDDP (1 wt%) and tert-butoxy (TBO) functionalized h-BN nanosheets [(h-BN-TBO), (0.02 mg/mL and 0.05 mg/mL)]. The addition of h-BN-TBO in ZDDP containing lubricant significantly improved the tribological properties due to the synergistic interaction between h-BN-TBO and ZDDP; leading to the formation of lubricious and robust antiwear tribofilms on Si and Al phase regions. A synergistic combination of h-BN-TBO and ZDDP as lubricant additive showed superior performance compared to ZDDP or a combination of ZDDP and MoDTC-based lubricant systems.