A microtexture study of eutectic carbides in white cast irons using electron back-scatter diffraction

Abstract

White cast irons have a microstructure composed of a ferrous matrix with hexagonal and/or orthorhombic carbides, M₇C₃ and M₃C, respectively. The US Bureau of Mines has implemented a study programme to improve microstructure and thereby wear resistance of these alloys. This work included electron back-scatter diffraction in a scanning electron microscope to identify the hexagonal and orthorhombic phases from their crystallography and subsequently establish their microtextures. Crystal structures of these carbides were identified and their microtextures were obtained from specific spatial locations within micrometre resolution. Such resolution allowed the identification of thin shells of M₃C (1–5 μm thick) to be distinguished from cores of M₇C₃ (10–20 μm thick). Microtexture results showed that M₇C₃ carbides without M₃C shells grew predominantly in the [0 0 0 1] direction, whereas those with M₃C shells were much less textured with the M₃C shell phase having a random microtexture.