Fatigue Strength of Steel Samples After Friction Treatment

Abstract

The work aims to study the influence of the tools’ shape of the working surface used during friction treatment of samples’ cylindrical surfaces on the formation of the strengthened layers and their effect on fatigue strength in the study on air and corrosion medium. The strengthened white layers with a nanocrystalline structure are formed in the samples’ surface layers during friction treatment. The research results of the influence of the frictional treatment on samples’ working surfaces made of Steel C45, Steel 41Cr4, and Steel CT80 (quench-hardening and low-temperature tempering) on fatigue strength during tests on pure bending with rotation in the air and corrosive media (3% aqueous NaCl solution) are presented. The thickness of the strengthened layer after treatment was from 120–130 μm to 180–190 μm. The microhardness of the strengthened layer is 1.7–1.9 times higher than the base metal. Residual compressive stresses are formed in the surface layers of the strengthened samples, which decrease with the depth of the layer. The fatigue strength of Steel C45 after friction treatment increased 1.4–1.7 times, Steel 41Cr4 – 1.3–1.5 times, and Steel CT80 – 1.4–1.6 times was shown by experiments. The fatigue strength has increased sharply and ranges from 3.4 to 4.2 times on Steel C45 and 6.7 times on Steel CT80, as shown in studies using the corrosive media. The obtained strengthened layers with a nanocrystalline structure can be used to increase the durability of parts with working cylindrical surfaces that work with cyclic loads in corrosive mediums.