Impacts of Bore Surface Finish and Coating Treatment on Tribological Characteristics of Engine Cylinder Bores 2002-01-1638

The impacts of cylinder bore surface finish and coating treatment on the tribological characteristics of engine components were determined by using a modified Cameron-Plint Friction and Wear Tester. The friction and wear behavior of several honed cylinder bores was compared using plateau-honed and brush-honed bores in a normal, lubricated sliding wear mode. Several experimental thermal sprayed aluminum bores, prepared following a water jet cleaning process, were compared to production cast iron plateau-honed bores. For the cast iron bores, it was observed that most of the wear occurred within the first 2 hours of the run-in stage. In general, the combination of a cast iron bore sliding against molybdenum sprayed piston rings showed lower friction and wear compared to the thermal spayed aluminum bore samples sliding against the same rings. The rough-honed bore samples demonstrated much higher wear than the plateau-honed or brush-honed bores. After initial break-in, the wear rate slowed down and asymptotically approached a constant value.

Wear mechanisms for cast iron bores include progressive oxidation, micro-attrition, and micro-abrasion. Wear modes for thermal sprayed aluminum bores are dominated by oxidation, abrasive wear, and splat delamination. A wear model using an organic-iron compound and oxide metal mixture was found to be useful in explaining the effects of surface treatments, additive interaction, surface finish, and tribological characteristics.