Nanoabrasive wear induced by an AFM diamond tip on stainless steel

Abstract

With the invention of the atomic force microscope (AFM) it became possible to study the wear phenomena at very small scales, from the micrometric to the atomic range. The AFM tips can be used to simulate a sharp single asperity travelling over a surface and nanowear experiments, at controlled contact pressures and scanning speeds, can be performed in almost any type of material. The same AFM enables to observe and characterize with a high lateral resolution the nano/microworn regions. In the present work, it is presented a preliminary study on the nanoabrasive wear response of a metallic alloy. AISI 316L, an austenitic stainless steel (SS) typically used for biotribological applications, was chosen as case study. A single abrasive asperity travelling on the SS surface was simulated by a hard AFM diamond tip, operating in contact mode. The nanowear tests were carried out with loads between 2 and 20 μN and scanning speeds between 2 and 80 μm/s in areas of 2 μm × 2 μm. It was observed that, under the present conditions, there is a load onset for wear, below what no measurable wear occurs. However, local modifications of the roughness and of the frictional response of the material, that can be detected by AFM techniques, point out that changes in the surface occurs before wear can be quantified. The experimental results also show that the wear rate increases with decreasing scanning speed of the diamond tip. Consequently, the results obtained in this work indicate that, in single submicrometric contact conditions, the abrasive worn volume of the material depends on the load, the number of interactions between the abrasive asperity and abraded surface and on the sliding speed.