Influence of deteriorated lubricants on friction modulation of micro-textured surface

Different lubricant deterioration, such as high-temperature oxidation lubricant (HOL), diesel dilution lubricant (DDL) and combined degradation lubricant (CDL), on the failure of micro-textured surfaces in terms of friction modulation was investigated. Deteriorated lubricant exerts obvious adverse effect on the antiwear performance of micro-textured surface, accelerating the wear damage of the tribopair consisting of a cast-iron liner and a molybdenum-sprayed ring. Compared to non-textured tribopair, HOL only increased wear loss of piston ring paired with micro-textured cylinder liners, while DDL containing diesel catalyst particles simultaneously increased the wear depth of both micro-textured cylinder liner and paired piston ring. CDL further exacerbated the DDL wear trend. The main type of damage caused by three degraded lubricants to micro-textured frictional surfaces was abrasive wear. Micro-textured surfaces trapped abrasive particles, separating the scratches along the sliding direction. But excessive stress concentration and scratches reduced the ability of ZDDP tribofilm to resist abrasive damage.