Structure of strengthening particles of niobium carbide in Fe–Cr–Ni cast refractory alloys

Abstract

Methods of optical and electron microscopies were used to study the structure of particles of niobium carbide in a cast refractory Fe–Cr–Ni–C alloy modified by Nb and Ti. Particles of niobium carbide in the structure of the cast alloy are predominantly multiphase polycrystalline clusters that are inhomogeneous in the chemical composition and crystal structure. The misorientation angle between individual crystals that compose the carbide particles is 30°–60°. The polycrystalline character of carbides is probably associated with significant thermal stresses that arise at the interphase boundaries in the structure of the alloy upon the primary cooling of the ingot. To explain the polymorphism of the cluster of niobium carbide, a further analysis of the structural and geometrical crystallography is required.