Nanoscale Anti-Wear Tribofilms — Prof. Robert W. Carpick University of Pennsylvania)

Prof. Robert Carpick discusses nanoscale anti-wear tribofilms and how they form in lubricants with additives: in-situ AFM studies, lubrication regimes (boundary/mixed/EHL), ZDDP vs. ZrO₂ nanoparticles, tribo-sintering, and their impact on wear, adhesion, micropitting, and scuffing. He also highlights the motivation for energy efficiency (reducing lubricant viscosity without losing wear protection) in applications like wind turbines and electric vehicles (EVs).
Key Takeaways
• Tribofilms from additives/nanoparticles form under shear stress and temperature; demonstrated with in-situ AFM.
• ZrO₂ nanoparticles create dense, hard films (tribo-sintered), effective even in pure rolling and at low temperatures.
• Cooperation with EP additives (phosphorus-containing) accelerates film growth and reduces wear compared to base oils.
• MTM/SLIM results show influence on friction coefficient, micropitting, scuffing, and film saturation time.
• Practical insights for gearboxes, bearings, wind turbines, and EV drivetrains.
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Related Resources on TriboNet
What is Tribology?
https://www.tribonet.org/wiki/tribology/
Friction: Basics and Mechanisms
https://www.tribonet.org/wiki/friction/
What is Lubrication?
https://www.tribonet.org/wiki/what-is...
Tribology Testing Standards (ASTM/DIN/ISO)
https://www.tribonet.org/tribology-te...
Pin-on-Disk Test — fundamentals of wear testing
https://www.tribonet.org/wiki/pin-on-...
Tribometers: Overview of instruments
https://www.tribonet.org/tribometer/
Surface Texturing — controlling friction and lubrication
https://www.tribonet.org/wiki/surface...
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Suggested Chapters (add timestamps as needed)
0:00 Introduction & motivation (energy efficiency, CO₂ reduction)
3:20 Lubrication regimes & Stribeck curve challenges
7:40 In-situ AFM method: observing tribofilm growth
12:30 ZDDP vs. ZrO₂ — mechanisms and film properties
18:00 Cooperation with EP additives and wear reduction
24:00 MTM/SLIM results: micropitting and scuffing
30:00 Applications: wind turbines, EVs, gearboxes
36:00 Q&A: growth kinetics, lubrication regimes, additive stability
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Discussion Questions
• How can tribofilm formation be accelerated in very short contacts?
• What role do thermal effects and non-Newtonian rheology play in growth kinetics?
• Can this approach enable 3D tribofilm profiling and inverse lubricant design?
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#Tribology #Lubrication #AFM #ZDDP #Nanoparticles #Zirconia #Wear #Friction #EHL #WindTurbine #EV