Preparation of in situ NbC-TiC@Graphene/Fe composite inoculant and its effect on microstructures and properties of GCr15

The NbC-TiC@Graphene/Fe composite inoculant was prepared by in situ reaction and high-energy ball milling techniques. The ceramic nanoparticles in the inoculant are surrounded by graphene and amorphous components. Compared with GCr15 without inoculation, the microstructure and mechanical properties of GCr15 bearing steel after inoculation treatment and heat treatment were studied. The inoculation treatment increases the nucleation rate of the as-cast microstructure, and the pearlite interlayer spacing and grain size are significantly reduced. After the heat treatment process, a fine cryptocrystalline martensite structure is obtained in the steel matrix. The graphene in the inoculant has an in situ reaction with Cr to form Cr7C3, and a small amount of austenite is present at the edge of the particle. The hardness, wear rate and tensile strength of the bearing steel after inoculation and heat treatment reached 61.2 HRC, 0.1904% and 2247 MPa, respectively. It is worth noting that the Impact toughness of GCr15 with inoculation reached 125.33 J/cm(2), which is 150.91% higher than that of GCr15 without inoculation. The relationship between macro-performance and microstructure is also clarified in this manuscript.