DRY SLIDING WEAR STUDY OF AISI HNY3 EXHAUST VALVE MATERIAL

Abstract

The effects of bearing pressure, sliding time, and sliding speed on dry sliding wear properties of AISI HNY3 internal combustion engine exhaust valve material were investigated. Experimental tests were performed by using a pin-on-disc apparatus. For all tests, pin was rubbed against silicon carbide emery paper of ASTM grit 180, which was mounted on rotary disc with varying speed 7.5 - 235.5 m/min, under varying bearing pressure 48.75 - 292.75 KN/m2.Experimental results, revealed that wear rates increased with increasing bearing pressure, in three linear regions separated by transition points. In the first region, wear rate were low , and increased slightly up to the first transition point, and the wear process was mainly controlled by formation of fine dark oxide debris particles, with smooth and flat wear tracks. This region falls in mild wear process. Beyond this point in the second region , wear rates were increased and debris particles became both metallic and oxidative, with rough wear track surfaces, and this region represents the transition zone from mild to severe wear. In the third region, wear rates were largely increased, and large metallic wear debris had been delaminated from the sliding surfaces, with rough and deep wear tracks in which severe wear had been formed. It was also concluded, that wear rates decreased with increasing sliding speeds.