Atom probe microanalysis of the γ phase in cemented carbide materials

Abstract

Atom probe field ion microscopy and analytical electron microscopy were used to study the γ phase (cubic carbide or carbonitride phase) in 85wt.% WC-8wt.%(Ti, W)C-7wt.%Co and 87wt.%-(Ti, Ta, V, Mo, W) (C, N)-13wt.%(Co, Ni). In both materials, γ phase grains consisting of a core surrounded by a rim of the same structure but different composition were common. Microanalysis revealed that the cores are grains which have remained undissolved during sintering and that the rims were formed by epitaxial precipitation onto the cores from the binder phase. In both materials a carbide (or carbonitride) skeleton had formed with half a monolayer of binder phase atoms segregated to the carbide boundaries.