Microstructure and mechanical properties of Fe/NbC composite layer prepared by in-situ reaction

NbC ceramic surface-reinforced steel matrix composites were prepared by an in-situ reaction method at different temperatures (1,050 °C, 1,100 °C and 1,150 °C) for different times (1 h, 2 h and 3 h). The phase constitution, microstructure and fracture morphology of NbC ceramic surface-reinforced steel matrix composites were analyzed by XRD, SEM and EDS, and the effects of the in-situ reaction temperature and time on the mechanical properties were systematically studied. The results indicate that the NbC reinforcement layer is formed through the reaction between Nb atoms and carbon atoms diffused from the steel matrix to the Nb plate. The thickness of this reinforcement layer increases as the reaction time prolongs. Additionally, an increase in reaction temperature results in a thicker reinforcement layer, although the rate of increase gradually decreases. The relationship among the thickness of the NbC reinforcement layer, the reaction time and temperature was established by data fitting. The optimal tensile performance is achieved at 1,100 °C for 1 h, with a tensile strength of 228 MPa. It is also found that the defects between the reinforcement layer and the steel matrix are related to reaction temperature. At 1,100 °C, these defects are minimal. Fracture mostly occurs in the NbC reinforced layer of the composites, and the fracture mode is characterized by typical intergranular brittle fracture.