Influence of Quenching and Partitioning on the Mechanical Properties of Low-Silicon 33MnCrB5 Boron Steel

Quenching and partitioning (QP) is a heat treatment that is designed to enhance both the mechanical properties and ductility of low- and medium-carbon steels. This treatment is performed on steels with a tailored chemical composition. Herein, QP treatments are designed and performed on commercial low-silicon 33MnCrB5 boron steel. Different temperatures (evaluated using thermodynamic simulations) and times are tested. Scanning electron microscopy investigations are conducted to observe the microstructure, whereas X-ray diffraction and electron backscattered diffraction analyses are performed to assess the presence and amount of retained austenite (RA). Tensile tests are performed to investigate the mechanical properties. The designed treatments introduce a fraction of up to 4.6% of RA in the final microstructure. Tensile tests show that the QP samples are characterized by high ultimate tensile strength (1633–1756 MPa) with an increased elongation at break with respect to the reference quenching and tempering condition (16–18% versus 9%). Hardening coefficients are linked to martensite tempering in the initial stages of plastic deformation, whereas at higher strains, they are mostly influenced by RA presence. The proposed treatments are successfully performed on 33MnCrB5 grade, leading to a set of tensile properties that are not exploitable with traditional treatments.