Search Results

Surface scuffing related to gas nitrided piston rings is attracting more attention as the effective cylinder pressure is increased in the recent years. However, the mechanism behind scuffing induced in long-term operations remained unknown. This study focuses on clarifying the mechanism behind scuffing related to gas nitrided piston rings. In addition, application of a thin composite plated surface film containing dispersed particles is proposed as an effective measure for preventing surface scuffing during long-term operations. Furthermore, factors enabling maintenance of high scuffing resistance on the ring surface after the thin plated composite film wears off and the underlying nitrided surface is exposed were analyzed. The dominant factor was discovered to be the difference in the resulting sliding surface profile, after initial wear, between a ring surface with composite plating and a ring surface with only gas nitriding treatment.

Friction and scuff resistance of ceramic coatings (K-ramic and ion plating) for rings was studied by using a basic wear test machine. Ceramic coatings have been recently remarked for their high heat and wear resistances. Friction force under firing condition was also measured by Furuhama's movable liner method to evaluate piston ring coatings. Ceramic coatings showed lower friction force than the conventional coatings of chromium plate and molybdenum spray coat. A durability test was also conducted to evaluate the wear resistance. Ion plating has the lowest friction with excellent wear resistance, and accordingly is a promising surface treatment for piston rings.