Analysis of carbides in multi-component white cast iron for hot rolling mill rolls

multi-component white cast iron was developed for rolling mill rolls. The morphology and alloy concentration of carbides precipitated during solidification were investigated using X-ray diffraction, SEM, TEM and EDS analysis in the cast iron with typical chemical composition of Fe-2%C-5%Cr-5%V-5%Mo-5%W-5%Co (mass%). When the iron solidifies, petal-like MC carbides with face-centered cubic lattices and plate-like M2C carbides with hexagonal lattices crystallize. During heat treatment, M2C carbide (hexagonal) reacts to gamma-Fe and transforms to M6C (fcc), M7C3 (orthorhombic) and MC (fcc) carbides, but the reaction is not followed by a change of carbide morphology. MC carbides mainly consist of V, and M,C, carbides are mainly formed by Cr and Fe. M2C carbides contain 20-25 atomic% each of Cr, V, Mo, and Fe, and 12 atomic% of W. M,C carbides are composed of approximately 33 atomic% of (Mo+W), and 50 atomic% of Fe and (Cr+V) in the balance.