A Review on Micropitting Studies of Steel Gears

Abstract

With the mounting application of carburized or case-hardening gears and higher requirements of heavy-load, high-speed in mechanical systems such as wind turbines, helicopters, ships, etc., contact fatigue issues of gears are becoming more preponderant. Recently, significant improvements have been made on the gear manufacturing process to control subsurface-initiated failures, hence, gear surface-initiated damages, such as micropitting, should be given more attention. The diversity of the influence factors, including gear materials, surface topographies, lubrication properties, working conditions, etc., are necessary to be taken into account when analyzing gear micropitting behaviors. Although remarkable developments in micropitting studies have been achieved recently by many researchers and engineers on both theoretical and experimental fields, large amounts of investigations are yet to be further launched to thoroughly understand the micropitting mechanism. This work reviews recent relevant studies on the micropitting of steel gears, especially the competitive phenomenon that occurs among several contact fatigue failure modes when considering gear tooth surface wear evolution. Meanwhile, the corresponding recent research results about gear micropitting issues obtained by the authors are also displayed for more detailed explanations.

Simulation of the fatigue-wear coupling mechanism of an aviation gear

“…As the surface roughness increased, a similar transition from sub-surface initiated failure to surfaceinitiated failure was also observed in Ref. [63]. Currently, the fine level of surface finishing with Rq below 0.2 μm can be achieved using a Fig.…”

A Micropitting Study Considering Rough Sliding and Mild Wear

“…Most recently, Liu et al [3] reviewed micropitting studies, which supports that the combined effect of the wear process and surface fatigue failure damages is of great significance on successful micropitting modelling. In particular, a competition mechanism between surface contact fatigue and mild wear has been revealed gradually over the last decade.…”

Tribofilm Formation, Friction and Wear-Reducing Properties of Some Phosphorus-Containing Antiwear Additives

“…These asperity stresses occur in high pressure contacts when surfaces are separated only by very thin lubricant films and are thus becoming more prevalent as lubricant viscosities are reduced in the quest for improved fuel economy. Although micropitting is primarily a mechanically driven process it has been found to be accelerated by ZDDPs [9][10][11]. This is because ZDDPs inhibit running-in, by forming tribofilms so rapidly that asperities present on the surfaces from manufacture do not have time to be smoothed or rounded.…”