Researches On Impact Fretting Wear Of Alloy 690 Tubes With Line Contact In Dry State

The steam generator is the core component of nuclear power systems in the primary and secondary circuit under heat conduction. Fretting wear caused by the flow of high temperature and high pressure medium between the heat transfer tube and the support plate is inevitable, so the life of the heat transfer tube decreases during the service process. This paper simulated and investigated the impact between the heat transfer tube and the support plates at different temperatures. The results of this study could enrich the basic theory of fretting. It has a guiding significance for improving the use of key components of nuclear power plant.In this paper, the test uses a self-made small impact testing machine and adopting the line contact mode between tube (690 alloy) and block (405 stainless steel) samples under dry condition. Adopting the optical microscope (OM),3D profiler (Contour GT-I), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) method to implore the wear mechanism, and the main conclusions were obtained as follows:(1) Under the room temperature conditions, the main impact wear mechanism of 690 alloy tube is consisted with oxidation wear, adhesive wear and peeling. With the load increasing, oxidation and adhesion wear are severe and loss of materials increases, so the service life of material is reduced. The O and Fe elements increased and the Ni and Cr elements decreased.(2) Under the room temperature, the impact wear of 690 alloy tube was very slight at the beginning stage. With the increase of the number of impact, the wear aggravated and the deformation accumulated along with the oxidation effect was enhanced.(3) Under the high temperature, the impact wear was slight at beginning stage, but it was more serious than that at room temperature. The wear surface oxidation layer formed very quickly, and the oxidation reached a stable state in a short time. With the increase of impact times, the wear width and the maximum depth increased, but the wear volume kept a steady value. The debris sintered in the wear surface and it formed a protect layer.