The effect of aging precipitation on the fretting wear behavior of 17-4 PH stainless steel used for tight fit assemblies

An experimental study on fretting wear behavior of a 17-4PH stainless steel aging heat treated to different microstructural features with different precipitate variants is presented. The fretting wear tests with respect to different fretting running regimes were carried out. The microstructural observations show that below 460°C of aging temperature, only NbC precipitates were observed. While as the aging temperature reached the 460°C, not only NbC but also Cu-rich precipitates (CRPs) can be found, and even more so at higher aging temperature. Wear results indicate that in the partial slip regime (PSR) and mixed fretting regime (MFR), the fretting wear volume decreases with the aging temperature increases up to 410°C, beyond which the wear volume commences to arise. The sample T2 (410°C) has a highest fretting wear resistance. In contrast, in gross slip regime (GSR), although the correlation of fretting wear volume and aging temperature shows a similar trend with that in PSR and MFR, the sample T3 (460°C) has a highest fretting wear resistance in GSR. It suggests that the precipitates have significant effect on fretting wear resistance, and their effects are fretting running regime dependent. Subsurface observations demonstrate that fine-size CRPs could promote the formation of the compacted and oxide-contained plastic deformation layer, which can improve the fretting wear resistance. The results can provide a good guideline to optimize the target microstructure for a specific working condition or tune the working condition parameter to allow a best fretting wear resistance.