WC-Fe layer with high volume fraction and fracture toughness on cast iron fabricated by in situ solid-phase diffusion

Abstract

A WC-Fe layer on cast iron was fabricated by in situ solid-phase diffusion method near the Fe–W–C ternary eutectic temperature. The phase composition and microstructure of the WC-Fe layer were studied by XRD, SEM, and EBSD. Meanwhile, the fracture toughness (KIC) of the layer was tested and calculated by indentation method. The results showed that the main phases were WC and α-Fe on the surface WC-Fe layer after removing excess tungsten plate, while the volume fraction of WC reached up to 86%. WC/α-Fe/WC laminar structure was formed due to the Fe atoms continued the stacking sequence of WC when they diffuse into the growth front. The cross-section microstructure showed evident gradient distribution characteristics. With the increase in holding time from 5 min to 135 min, the amount of Fe6W6C decreased, and the particle size of WC increased from 1.9 μm to 3.1 μm in the average. The KIC of the WC-Fe layer was 7.45 MPa m0.5, while the average hardness of WC-Fe layer was 16.88 GPa. The excellent KIC of the WC-Fe layer when the volume fraction of WC was extremely high due to WC-Fe-WC laminar structure, was formulated by the incorporation of WC-layered growth and Fe atom stacking mode.