Correlation Between Roughness, Film Thickness and Friction Coefficient with Pitting Wear Resistance of Spur Gears

Abstract

Abstract The present investigation aims correlate the roughness, film thickness and friction coefficient with pitting wear resistance along the rolling-sliding contact fatigue of forged and plasma nitrided gears. The hypothesis of this work is that the pitting wear resistance of forged gears can be greatly improved by pulsed plasma nitriding. Weibull’s statistical analysis confirms that nitrided gears with 24 vol.% N2 showed the lowest pitting wear rates among the investigated conditions, which was attributed to the best combination between surface hardness, fracture toughness, compound layer thickness, and phases on surface. The pitting wear intensifies with increasing roughness, but this same behavior was not observed between the wear evolution and the maximum shear stress field in the sub-surface. Another interesting fact is that nitrided gears with 24 vol.% N2 (best condition), have a greater film thickness at the end of the rolling-sliding contact fatigue, which gives it greater protection, less friction and pitting wear.