Observation of fretting fatigue cracks of Ti6Al4V titanium alloy

Abstract

Using a test system developed in laboratory, the fretting fatigue mechanism of Ti6Al4V alloy has been studied, with analyses of fracture morphology and composition. The results show that fretting fatigue source area is semi-elliptical and occupies a small proportion of the total fracture surface. The area is relatively flat and smooth and shows traces of friction. With the increase of contact pressure, the depth of the source region first increases rapidly and then stabilizes, but the fatigue strength decreases rapidly and then stabilizes. Fretting causes severe oxidation of the surface. In the interface between the source and the fatigue propagation zone, the contents of O and Fe drop sharply.

Influence of Ultrasonic Surface Rolling Process and Shot Peening on Fretting Fatigue Performance of Ti-6Al-4V

“…The coupling effect of the above three parameters greatly improves the fretting fatigue life.In the stress range of 600~650Mpa, SP does not significantly improve the fatigue life of Ti-6Al-4V. The research on the effect of SP on the fatigue strength of cast iron structure shows that higher residual compressive stress and nanocrystalline structure help to improve the fatigue strength, but the high roughness caused by SP will greatly weaken the above effect [32]. Generally speaking, parts with larger friction coefficients are more susceptible to fretting damage, especially titanium alloys that are more sensitive to fretting wear.…”

Microstructural evolution and oxidation in α/β titanium alloy under fretting fatigue loading

“…Furtherly, recrystallized nanostructures could be well established with negligible residual plastic strain inside [24]. However, fretting fatigue cracks prefer to nucleate along the highly deformed band beneath the contact site [26], and the grains adjacent to the fretting fatigue crack extension path are severely strained and exhibit high grain reference orientation deviation (GROD) values [27]. The dynamic recrystallization process of grains in the TDL from initial coarse structures to well-established nanograins has not been fundamentally studied in the literature, leaving a gap in understanding the fretting damage of metallic materials.…”

“…Moreover, the oxygen enrichment in crack formation and early propagation domains indicates a significant role of tribo-oxidation in nucleating fretting fatigue cracks [27]. Nevertheless, the oxygen diffusion activity of materials that undergo tribo-deformation remains elusive.…”

The role of a thermally sprayed CuNiIn underlayer in the durability of a dry-film lubricant system in fretting – A phenomenological model

“…The fan blade/ disk dovetail in an aero-engine system is a highly loaded contact subject to mechanical vibration. Relative motion at the contact can lead fretting wear and fretting fatigue [1][2][3][4][5] . In this application both components in the contact are typically made from titanium alloys and, due to the poor tribological behaviour (high coefficient of friction and high rate of wear) of self-mated titanium alloys, a number of surface engineering approaches to combat fretting damage have been developed.…”