Investigation of fundamental wear mechanisms at the piston ring and cylinder wall interface in internal combustion engines

This research examined the cylinder liner-piston ring system simultaneously from the metallurgical and metrological standpoints, using specimens cut from real engine components (rings and liners), in order to identify the mild and severe wear mechanisms. Work has been conducted using a Plint TE77 high frequency friction machine. Metrological analysis was performed using stylus contacting profilometer. Metallurgical analysis of the samples was carried out using a JOEL JSM-6400 scanning electron microscope. In addition to wear, the coefficient of friction (mu) was recorded for every piston ring -cylinder liner pair so as to observe the transitions between mixed and boundary lubrication. This paper presents the results obtained using flame sprayed Mo-coated spheroidal graphite cast iron, which is an old piston ring coating and is not available anymore, and relatively new Federal Mogul CKS-36 (TM) top compression rings tested against a grey cast iron cylinder liner tested at two different bulk oil temperatures (90 degrees C and 140 degrees C), two different pressures (3.9 MPa and 6.5 MPa) and with two different lubricants (SAE 0W20 with a Friction Modifier and SAE 15W40).