2019 年 60 巻 6 号 p. 1011-1017
High chromium cast irons show superior abrasion resistance due to their chromium carbides. Their abrasion resistance is improved by insert casting with cemented carbide. The effects of high-temperature exposure during insert casting on the microstructures of cemented carbide were investigated in this research. The high chromium cast iron (2.7%C–27%Cr) and the cemented carbide round bars (WC–13.7%Co) were prepared. The round bars were dipped in molten high chromium cast iron at 1596 K. The dipped round bars were pulled up after the elapse of 30–180 s. Microstructures of dipped round bars were changed from homogeneous sinter structure to three-layer structure, cemented carbide, diffusion layer, and reaction layer. The thicknesses of the diffusion layer and the reaction layer were increased with increasing of dipping time. FE-EPMA analysis revealed that the diffusion layer was formed by the elution of Co from the cemented carbide and diffusion of Fe and Cr from the molten high chromium cast iron into the cemented carbide round bar. In addition, rectangular particles were randomly distributed in the diffusion layer. The equivalent circular diameter of the rectangular particle was increased with increasing dipping time. The Vickers hardness of the diffusion layer decreased about 30% relative to the cemented carbide but higher than that of high chromium cast irons. The inserted cemented carbide is thought to have contributed to improving abrasion resistance. It was suggested that thin diffusion layers are more effective for improving abrasion resistance.
This Paper was Originally Published in Japanese in J. JFS 90 (2018) 217–223. The abstract, background, experimental procedures, results and discussion have been revised.
