A 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 platelike M 2 C carbides with hexagonal lattices crystallize. During heat treatment, M 2 C carbide (hexagonal) reacts to g-Fe and transforms to M 6 C (fcc), M 7 C 3 (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 7 C 3 carbides are mainly formed by Cr and Fe. M 2 C carbides contain 20-25 atomic% each of Cr, V, Mo, and Fe, and 12 atomic% of W. M 6 C carbides are composed of approximately 33 atomic% of (MoϩW), and 50 atomic% of Fe and (CrϩV) in the balance.KEY WORDS: white cast iron; rolling mill roll; alloyed carbide; carbide reaction. ed in turn, and one section was austenitized at 1 273 K for 54 ks, hardened by fan air cooling to room temperature, and subjected to double tempering at a repeated 798 K for 54 ks (hereinafter referred to as hardened-tempered treatment).At the positions 50 mm away from the bottom end and 10 mm from the periphery of each specimen, rectangular specimens 10 mm square and 20 mm long were cut out in radial direction. After observation of microstructure by a scanning electron microscope (SEM), carbides were identified by means of X-ray diffraction and TEM with an accelerating voltage of 200 kV. Alloy concentrations were measured by an energy dispersive X-ray spectrometer (EDS) with an accelerating voltage of 200 kV and beam diameter of 20 nm. For TEM observation, extracted replicas were prepared by cutting the rectangular specimen to 0.5 mm thick sheet, polishing the sheet down to 50 mm in thickness with emery paper, punching the polished sheet to a disk 3 mm in diameter, thinning the disk to the film by alumina polishing, and etching the film by the SPEED method (Selective Potentiostatic Etching by Electrolytic Dissolution method). Figure 1 shows SEM microphotographs of the specimens in as-cast, annealed and hardened-tempered states. In all specimens, nodular or petal-like (hereafter generically described as nodular) MC carbides 5 to 20 mm in diameter crystallized in and at the grain boundaries of pro-eutectic austenite; and rod-like or plate-like (hereafter generically called plate-like) M 2 C carbides 10 to 50 mm in length crystallized at grain boundaries. The outward appearance of the plate-like carbides is analogous in all the specimens. While the plate-like carbides are white and single phase in the ascast state, those in the annealed specimen are rugged at the periphery and they show a mixture of white-and-gray phases under a high magnification, though they seem to be an aggregate of small particles under a low magnification. Figure 2 and Table 2 show the results of carbide identificati...
