多合金系白鋳鉄における析出炭化物の解析

抄録

  The type and alloy concentration of precipitated carbides in matrix were investigated using X-ray diffraction, SEM, TEM and EDS analyses in multi-component white cast iron with typical composition of Fe-2%C-5%Cr-5%V-5%Mo-5%W-5%Co (mass%). MC, M₂C and M₇C₃ carbides already exist in the as-cast state. M₆C and M₇C₃ carbides are precipitated during annealing, and carbides existing in the hardened-tempered state are MC, M₆C and M₇C₃ types. In the as-cast state, two types of crystal lattices were confirmed in the MC carbide, mostly face-centered cubic (FCC) and partly hexagonal. The MC carbides contain V by more than 65at%. M₂C carbide with hexagonal lattice contains 35at% of Cr and Mo, and 12at% of V and W. M₆C carbide with FCC lattice consists of 44at% of (Mo+W) and 45at% of Fe. M₇C₃ carbide has orthorhombic lattice, but shows different shapes ; string-shape in the as-cast and hardened-tempered states and oval in the as-annealed state. The M₇C₃ carbide is mainly formed from Cr and Fe.