Investigation of the Effects of Soot on Friction and Wear Characteristics of Polymers (Elastomers and Thermoplastics) Engine Components

Over recent years, there has been an increase in the level of soot in an engine attributing to the friction and wear of engine components. This has caused challenges to the automotive industries to develop advanced lubrication or use other materials for engine components that can withstand friction and wear problems in order to increase the performance of an engine. The cause of the increase of soot levels in an engine is the technological development that requires a decrement of pollutants emitted to the air in respect to the emission policy; as well as the need to reduce the maintenance costs by extending service intervals. Many previous research studies have been conducted to see the effect of soot on ferrous materials, using laboratory specimens and real engine components. And there is vast research on nonferrous materials using abrasive particles; however; the effect of soot on nonferrous materials is still lacking. This study aims to investigate the effect of soot on nonferrous material such as polymers. Nonferrous materials are seeing increased use in engines so it is important to understand how they behave with soot as abrasive particles. To achieve this, the working performance of different material specimens particularly O-rings has been evaluated using ball-on-flat and block-on-ring tribometer. This specific component is chosen to mimic the valve stem O-ring contact condition inside an engine. Results obtained in this work indicate that the major wear mechanism for all materials is abrasion with respect to increasing of carbon black content inside the lubricant with some material removal due to fatigue cracking for thermoplastics materials and signs of deformation and particles embedment in elastomers ones. It can be said that the friction and wear is dominated by material properties for elastomer materials while for thermoplastics materials; the friction and wear is affected by the lubricant, soot and other contact parameters such as load and temperature.