Investigation On Micro-Amplitude Impact Wear Characteristics Of Alloy690at Room Temperature

In nuclear power plants’s operation process, flow induced vibration is an important factor that leads the interaction of the steam generator heat transfer tubes and support plates or anti-vibration bar.And the gaps were designed and manufactured between the heat transfer tubes and support plates or anti-vibration bar.Therefore,there will be micro-amplitude impact wear between them in operation process. Which can cause the wear of heat transfer tubes,even thinning or cracking failure.The cause and mechanisms about the impact wear and cracking failure of690alloy are revealed by simulating micro-amplitude impact load imposed on the surface of heat transfer tubes.The results of the study can provide some theoretical support for mastering the mechanisms of the impact wear caused by flow induced vibration and correlation failure analysis,and therefore this study has very important scientific significance and realistic engineering value.A tube-plate line contact wear model was conducted in this study and wear tests were carried out in a small load impact wear tester.Different lengths of690heat transfer tubes and405stainless steel flats were selected as the tested materials,combined with white light interferometry, optical microscopy(OM),scanning electron microscopy (SEM),micro hardness tester,energy dispersive spectroscopy(EDX),X-Ray Photoelectron Spectrometer (XPS)analysis of the parameters,material properties and wear performance of the test sample, the conclusion is as follows:1. The tube lengths has a significant influence to the experimental results.The longer tubehad larger the stiffness and better performance of anti-alternating bending fatigue.The damage mechanism was wear. The shorter tube had smaller stiffness, and the fatigue cracking was the damage form.2. Under maller load, oxide layer appeared in the heat transfer tubes and it then formed a delamination layer,finally leaded to wear-material loss.Under higher load,the oxide delaminlation layer was found at the wear surface. On other hand, larger stressresult in the surface material is squeezed and occurrence of dislocation slips in the surface material and cracking.3. Under water environment, the material damage was significantly lower than dry condition.One of the reason maybe the presence of the water film has a damping effect, and it obviously reduced the surface stress. The other reason maybe the low Oxygen content in water condition make few oxidation layer and cracking need a larger load than that appear in dry condition.