Fretting is a surface-degradation process due to mechanical and chemical attack by small-amplitude oscillatory movement between two contacting surfaces and it is intimately related to wear, corrosion and fatigue. Stainless steel(SS316L) are often used in nuclear industry, especially in sodium-cooled nuclear power plants, because of their excellent mechanical properties under high temperature and irradiation environment, but are characterized as having relatively poor wear and galling resistance. For fast breeder reactors sodium provides a relatively benign environment for most structural materials. Sodium is a highly reactive element that tends to strip the oxide films from most metal surfaces, leaving them in ultra clean condition. This promotes adhesive wear, high friction and self-welding tendencies that are similar to those observed in a high vacuum. As part of the present study, experimental investigations were carried out for displacement amplitude varying from 50microns to 200microns with a normal load of 70N under ambient and high vacuum conditions (10~(05)mbar) . Self-mated stainless steel (SS-316L), Chromium carbide with 25% Nickel chrome binder coatings using plasma spray and High velocity oxy-fuel (HVOF) processes on SS316-L were used for the studies. Mechanical responses in the form of variation of coefficient of friction (COF) with number of cycles and displacement amplitude were analyzed. Qualitative evaluation of damage has been carried using Scanning Electron Microscope (SEM) and quantified based on variation of wear volume with displacement amplitude. Chromium carbide with 25% Nickel a chrome binder coating using HVOF processes on SS316-L showed less fretting damage under vacuum condition and is expected to be an effective solution against fretting damage.
展开▼
