WC-18Co reinforced Iron matrix composites: Microstructure and interface characteristics

Abstract

Particle reinforced iron matrix composites have gained considerable attention as advanced structural materials. In this study, large-sized WC-18Co reinforced iron matrix composites were prepared using the casting infiltration method. We investigated the microstructure and interface characteristics of WC-18Co/FMC, analyzed the stress state at the interface, and tested the mechanical and tribological properties of the composite material. The research findings reveal that WC-18Co/FMC is a multiphase system composed of WC, M3W3C (M = Fe, Co), and precipitates. The strong interface reaction results in the formation of a thick transition layer between WC-18Co and the matrix. Grain refinement occurs around the reinforcing particles. During solidification, the difference in thermal expansion coefficients between WC-18Co and FMC induces thermal stress, leading to compressive residual stress on both sides of the interface. The compressive stress state inhibits crack initiation and propagation, enhancing the bonding strength. Alternating stresses at the interface enhance dislocation motion, grain slip, and twinning phenomena in the transition layer. Nanoscale compounds embedded in the transition layer impede dislocation slip, resulting in dislocation entanglement and pile-up. WC-18Co/FMC exhibits a 60.66% increase in hardness compared to FMC. Under impact energies of 1 J, 3 J, and 5 J, the wear resistance improves by factors of 2.985, 2.358, and 2.072, respectively. The significant improvement in the composite material's performance is attributed to strengthening mechanisms such as the multiphase system, grain refinement, nanoscale precipitates, and residual stress strengthening.