The effect of Si on the relationship between orientation and carbide morphology in high chromium white irons

Abstract

Electron back-scatter diffraction (EBSD) has been shown to be the most appropriate technique to study the orientation and carbide morphology of small (<0.5 μm) regions of microstructure of high chromium white irons. The carbides in a slightly hypo-eutectic Fe–Cr–C alloy show a distinct texture close to [1 0 1 1] whereas those in a 1.3 wt% Si commercial white iron have a diffuse texture, with regions near to major crystal directions, i.e., [0 0 1 1], [1 2 1 0], [0 1 1 0], unpopulated. Using EBSD, it has been shown that the interconnectivity of the eutectic (Cr, Fe)7C3 carbide is less in a 1.3 wt% Si alloy compared with a low (0.1 wt%) Si alloy. This reduced interconnectivity is consistent with the increased fracture toughness in the as-cast condition.