Changes in microstructure and mechanical properties during the bending process of NM450 wear-resistant steel

Abstract Bending deformation is a typical forming method in the manufacturing process of mechanical equipment. NM450 wear-resistant steel with high strength is vulnerable to bending failure, thus decreasing the bendability. The changes in microstructure and mechanical properties of NM450 wear-resistant steel during the bending process were studied by scanning electron microscopy, energy dispersive spectroscopy, optical microscopy, transmission electron microscopy, electron backscattered diffractometer methods, and tensile test. The inner and outer arcs around the bending axis underwent compressive stress and tensile stress, respectively, causing an obvious bending deformation of the martensite laths with a high dislocation density. The tensile strength around the inner- and outer-arc of samples exceeded that at the mid-thickness. During the bending process, the microsized TiN inclusions nearby the outer arc were subjected to tensile stress and multiple microcracks/cavities perpendicular to the outer arc were formed. However, the microsized TiN inclusions nearby the inner arc underwent compressive stress, initiating the occurrence of divergent microcracks.