Micro-Pitting and Wear Assessment of PAO vs Mineral-Based Engine Oil Operating under Mixed Lubrication Conditions: Effects of Lambda, Roughness Lay and Sliding Direction

• Main Authors: Aleks Vrček, Tobias Hultqvist, Yannick Baubet, Marcus Björling, Pär Marklund, Roland Larsson
• Format: Article
• Language: English
• Published: MDPI AG 2019-05-01
• Series: Lubricants
• Subjects: micro-pitting; ZDDP; mild wear; surface-initiated fatigue
• Online Access: https://www.mdpi.com/2075-4442/7/5/42

Under certain operating conditions, rolling contacts have been shown to experience some challenges when lubricated with engine oils containing zinc dialkyldithophosphate (ZDDP) anti-wear additive. In order to better understand the main damage mechanisms during various operating conditions, further studies are needed. This article studies micro-pitting and wear damages of bearing steel surfaces under mixed lubrication conditions in a ball-on-disc setup, lubricated with different engine oils. Based on the results, micro-pitting and wear damage is shown to be highly case-dependent. In general, PAO-based engine oil tends to eliminate micro-pitting damage compared to mineral-based engine oil at less severe lubricating conditions. Moreover, a critical lambda was found for both oils, where the highest micro-pitting damage was observed.