Mechanical properties of a spray deposited bearing steel

Typical features of spray deposited steels are a homogeneous isotropic microstructure without any segregation, a porous region at the billet border and coarse grains in the core of the billet. To overcome coarse grain and porosity, a subsequent hot rolling and a following heat treatment is necessary. For the present work, the bearing steel SAE 52100 was used as a master material. By hot rolling, the initial microstructure was transformed to a homogeneous equiaxed fine-grained pearlitic microstructure without any remaining porosity. To get use of the characteristic properties of this high-strength steel, an isothermal bainitic hardening was carried out which again leads to a very homogeneous and isotropic microstructure. Information about the mechanical properties of this material was gained by tension and fatigue tests. Due to the isotropy of the microstructure, high fatigue resistance is not only observed for axial, but also for loads perpendicular to the rolling direction.