Development of ultrafine bainite plus martensite duplex microstructure in SAE 52100 bearing steel by prior cold deformation

We explore microstructural refinement through complete/partial recrystallization of prior cold-deformed ferrite during austenitizing or austempering of SAE 52100 steel to obtain ultrafine bainite and martensite. Optical and scanning/transmission electron microscopy coupled with compositional microanalysis were employed to determine the volume fraction and dimension (thickness/length) of ferritic sheaves and carbides. Characterization of mechanical properties indicates that 5-15% cold deformation significantly enhances the impact strength (similar to 72 J) with marginal improvement in hardness and tensile strength over that in the undeformed condition. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.