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.

https://www.mdpi.com/2079-6412/9/1/42/pdf

A Review on Micropitting Studies of Steel Gears

A model to predict initiation and propagation of micro-pitting on tooth flanks of spur gears

Ratchetting–multiaxial fatigue damage analysis in gear rolling contact considering tooth surface roughness

Effect of retained austenite on micropitting behavior of carburized AISI 8620 steel under boundary lubrication

AISI 4140 powder was directly deposited on AISI 4140 wrought substrate using laser engineered net shaping (LENS) to investigate the compatibility of a LENS-deposited part with the substrate. Tensile testing at room temperature was performed to evaluate the interface bond performance and fracture behavior of the test specimens. All the samples failed within the as-deposited zone, indicating that the interfacial bond is stronger than the interlayer bond inside the deposit. The fracture surfaces were analyzed using scanning electron microscopy (SEM) and energy disperse X-ray spectrometry (EDS). Results show that the tensile fracture failure of the as-deposited part is primarily affected by lack-of-fusion defects, carbide precipitation, and oxide particles inclusions, which causes premature failure of the deposit by deteriorating the mechanical properties and structural integrity.

B.A. Shaw

Papers

Experimental and analytical study of gear micropitting initiation and propagation under varying loading conditions