Running-in for Low Friction between Silicon-Containing Aluminum Alloy and Bearing Steel in Engine Oil

The friction properties of an aluminum-silicon alloy (Al-Si) can be improved by increasing its silicon content. However, this deteriorate the material necessary for engine components. Therefore, alternative approach to reduce is required. This study investigated running-in behavior, reduction from initial stable phase sliding, between Al-Si with varying contents and bearing steel in fully formulated oil. silicon-free aluminum (Al) was classified into three modes: no (mode I), after a high-friction period II), immediate III). Al exhibited only mode I, low-silicon-content mainly displayed II, high-silicon-content III. Energy-dispersive X-ray spectroscopy revealed that, zinc dithiophosphate (ZnDTP) reacted matrix, suppressing adhesion forming molybdenum-dithiocarbamate-derived tribofilm. Nanoindentation micro-Vickers tests demonstrated that high hardness matrix did not increase ZnDTP reactions. friction-induced hardened layer on promoted reactions, suggesting key factor low-friction interface without