Researches On Tangential Fretting Wear Of Alloy690Tubes With Line Contact In The Dry And Different Temperature State

In the core components of nuclear steam generator system, the fretting wear phenomenon can’t be avoid with the interaction of the steam generator tubes and the support plates, In addition, the service condition is usually at very high temperature. This thesis studies the fretting damage behavior by simulating the fretting wear between the heat transfer tubes and the support plates. This study has an application value for the development of fretting tribology basic theory and the improvement of service performance of the important components in the nuclear power plants.MFF-3000electromagnetic vibration fretting wear tester and PLINT fretting wear tester were used in this study. The tangential fretting wear tests were carried out on the China-made690alloy tubes and405stainless steels samples and under dry state under line contact. The damage behavior of the test samples was analyzed binding optical microscopy (OM), three-dimensional morphology instrument, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX). The main conclusions are showed as the following:1. When the normal load was10-80N, the displacement amplitude was5-100um, and the frequency was30Hz, the partial slip regimes and slip regimes were observed and the mixed fretting regime was not observed at room temperature. In partial slip regimes there were very slight wear or discontinuous wear scars on the surfaces of the sample tubes. The wear mechanism was abrasive wear and stripping layers in some parts. In slip regimes the wear scars on the surfaces of the sample were severed, and the wear increased with the increase of the displacement amplitude. The wear surfaces were covered with debris and accumulation layers, and the degree of oxidation of the worn surface was more serious. The wear mechanism was the stripping layers, and abrasive wear could be observed.2. When the normal load was10N,20N and40N, the displacement amplitude was100μum and200μm, and the frequency was5Hz, the fretting of the690alloy ran on slip regimes at room temperature. The stable friction coefficient under the load of10N and20N was larger than that of40N. The wear loss increased with increasing loads. The wear mechanism was stripping layers, oxidation wear and abrasive wear. Under the conditions of10N, the degree of oxidation of the worn surface was much lower than the conditions of20N and40N.3. When the normal load was40N, the displacement amplitude was100μm and200μm, and the frequency was5Hz, the fretting of the690alloy ran on slip regimes at the temperatures of25℃,90℃,200℃and285℃. The stable friction coefficient and the wear amount arrived at the largest value at90℃. At a lower temperature (25℃and90℃) conditions, the width of wear scars were large, and the worn surfaces were covered with oxidized debris layers. At a higher temperature (200℃and285℃) conditions, the wear was lighter than the lower temperature. There were furrows and flaking pits on the worn surfaces. By the cross section observation, two edges of the wear scar appeared to be heave at200℃; the tight debris layers above the contact surface was appeared at285℃. The EDX results showed the higher oxygen peaks at the lower temperatures, which might be the different oxidation behavior occurred in the interface between the lower and the higher temperatures.