Effect of In Situ NbC Volume Fraction on the Microstructure and Erosion Resistance of 4Cr5MoSiV1 Matrix Composites
摘要
Self-generated ceramic particle-reinforced steel matrix wear-resistant composites exhibit enhanced wear resistance due to their superior interfacial bonding capability; the experimental conditions selected for this study were erosion velocities of 25 m/s and 51 m/s, an erosive medium consisting of a mixed SiO2 and NaCl solution, NbC (Niobium Carbide) volume fractions of 0%, 1%, 3%, and 5% in NbC/4Cr5MoSiV1 composites, an erosion angle of 90°, an erosion nozzle diameter of 2 mm, and a standoff distance of 40 mm. NbC/4Cr5MoSiV1 composites with varying NbC volume fractions were fabricated via in situ synthesis to investigate the influence of NbC volume fraction on the composite microstructure and erosion wear resistance; the study revealed that with increasing volume fraction, NbC transitions from a network-like precipitate at grain boundaries to particulate distribution both at grain boundaries and within grains, while composite hardness increases from 397.8 ± 71.4 to 826.2 ± 95.7 HV. Under erosive wear conditions, the erosion resistance of the composites was 2.42 to 3.44 times that of the matrix, and both erosion pit depth and diameter decreased with increasing NbC volume fraction; the primary erosion wear mechanisms involve micro-cutting of the composite by abrasives and fracture/spallation of NbC particles. This experiment aims to investigate the erosion–corrosion wear performance of NbC4Cr5MoSiV1 composites with different NbC volume fractions in corrosive environments, elucidate the differential impact of erosion velocity (25 m/s, 51 m/s) on material failure modes, and achieve mechanistic innovation through a four-dimensional (corrosion–erosion–velocity–composition) coupling study. Existing literature primarily focuses on the macro-scale wear resistance improvement by NbC and has not established the cross-scale correlation linking NbC distribution morphology (network → particulate) → interfacial bonding strength → fatigue life in corrosive environments. This study specifically contrasts the failure modes of the NbC reinforcement phase under low-velocity (25 m/s) and high-velocity (51 m/s) erosion, clarifying the correlation between phase spallation induced by high-speed impact and corrosion acceleration. NbC/H13 composites cost merely one-third of cobalt-based alloys. The distribution of NbC particles was tailored by controlling parameters during in situ synthesis; they enable domestic substitution in applications like shield machine cutter rings and marine pump/valve components, significantly extending service life.