Some power transmission components are subject to fretting corrosion failure mode which results in early wear of the mating surfaces or premature fatigue crack initiation. The fretting corrosion is generated by micro-movements of surfaces in contact. In mechanical transmissions, it can be found in particular at the level of shrink-fit connections (bearing rings for example) and key and spline connections when they are misaligned.
The french commission of mechanical transmissions and bearings and Cetim are studying the capacity of technical solutions to delay the fretting damage (materials, treatment, lubrication, ...). This article presents the study of the impact of thermal and thermochemical treatments of steels used in power transmissions on the appearance, morphology and intensity of corrosion fretting.
Among the usual materials and treatments in mechanical transmission (NF EN 683, ISO 6336-5), the following variants have been studied: through hardened (42CrMo4, 100Cr6), steels treated by surface quenching (42CrMo4), case hardening steels (20MnCr5) and nitrided steels (42CrMo4). These variants are compared using a standard ASTM G204 test which consists in oscillating a pin (here in 100cr6) under pressure and without lubricant on a plate (tested variant) for a period of 24 hours. The range of displacement is fixed at 50µm or 100µm depending on the variant. The tangential forces during the tests, then the mass and the topography of the impressions of the pins and plates after test are measured, analyzed and compared.
The experimental study highlights wear mechanisms and typologies that differ between the variants of thermal and thermochemical treatments and the amplitudes of microslip.