Surface Properties of Tailored Forming Thrust Bearings

The surface properties of rolling bearings are fundamental to avoid wear and early failures. In our case, Tailored Forming cylindrical thrust roller bearings were investigated. Through laser cladding or plasma-transferred-arc welding, a lower grade base steel can be combined with a high strength steel acting as cladding for rolling contact loads. A subsequent forging process is applied to benefit from process- and material-specific advantages. Fatigue tests were conducted to assess the bearings. Prior and after the tests, the bearing surfaces were investigated by nano-indentation studies. Nano-scratch tests were performed to determine the frictional and mechanical surface properties. The measurements were carried out on a Bruker (formerly Hysitron) TI950 TriboIndenter by applying a spherical diamond cone tip with a radius of 300 nm. The travel length of the tip on the surface was 8 µm. Each test was performed in three steps: initially, the surface contour was scanned by the tip under very low load on one path (pre-scan). Next, the scratch was performed on the same route with a final force of 1 mN (scratch). Finally, the plastically deformed material was analysed in a post-scan. During the test, the coefficient of friction was evaluated. The measured surface properties were compared to thrust bearings made from conventional 100Cr6 bearing steel.