Friction and Wear Behavior of Austenitic Stainless Steel: Influence of Atmospheric Humidity, Load Range, and Grain Size

Research conducted on steels is motivated by a technological need to further improve their properties. Among the different steel types, austenitic stainless steels possess good corrosion resistance and formability. However, they also have a relatively low yield strength. One way of increasing the yield strength is by grain refining. This work presents a study on the effect of relative humidity and applied load range on the friction and wear of AISI 304 austenitic stainless steel characterized by two different grain sizes: 2.5 and 40 μm. Using a precision microtribometer, with applied loads in the μN regime, it was found that capillarity plays a dominant role. At the same loads, in high humidity environments, both the fine and coarse grain steels exhibit high friction relative to measurements performed under dry conditions. At loads greater than 2 mN a reversal in microfrictional behavior occurs in that microfriction was greater under dry conditions than under moist conditions. At loads of 2 N, using a standard ball-on-disk tribometer, severe wear was evident at low humidities while relatively lower wear was observed at high humidities indicating a lubricating effect of water.