Tribological performance of three advanced piston rings in the presence of MoDTC-modified GF-3 oils

• Published in: Tribology letters Vol. 18; no. 1; pp. 75 - 83
• Main Authors: Yajun, Ma, Wancheng, Zhao, Shenghua, Li, Yuansheng, Jin, Yucong, Wang, Simon, Tung
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.01.2005
• Subjects: Assembly; Boron carbide; Cast iron; Coefficient of friction; Cylinders; Internal combustion engines; Maintenance management; Mechanical properties; Morphology; Motor vehicle fleets; Piston rings; Stainless steels; Tribology; Wear
• DOI: 10.1007/s11249-004-1759-6
• ISSN: 1023-8883

The piston assembly (piston ring and cylinder bore) is one of the key parts of the internal combustion (IC) engine. Its performance will directly determine the performance of the whole engine. The piston assembly’s tribological performance will be influenced by both its mechanical properties and the tribochemical interactions that take place on their surfaces. In this paper, three kinds of advanced stainless steel piston rings with a single nitrided layer, CrN coating on the nitrided layer and a B4C and CrN binary-layer coating on the nitrided layer, respectively, were employed. Their frictional behavior and wear performance, when sliding against the cast iron cylinder bore materials lubricated with two kinds of GF-3 category mineral-based engine oils (one of them blended with MoDTC friction modifier), were investigated on a SRV tribotester. The test conditions were set and maintained to simulate engine-operating conditions. SEM (Scanning Electron Microscopy) and EDX (Energy Dispersive X-ray spectroscopy) were employed to characterize the morphology and elemental composition of the wear tracks. Tribotests and analysis results indicate that changes in both the mechanical properties of the tribomate (piston coatings) and tribochemical interactions (formulation of engine oils) have an impact on the tribological performance of the piston assembly. Tribochemical interactions will have a more obvious influence on friction coefficients while the mechanical properties of the tribomate have a more obvious influence on wear.