Role of copper in iron–iron boride cermets

Abstract

Multiphase sintering of an iron, copper and boron powder mixture of a concentration of 5–15 wt.% of copper and 9 wt.% of boron has been analysed. It was found that an addition of copper to a powder mixture allows full control of the quantity of liquid phase during the sintering by the mass concentration of Cu. Structure and properties of the generated cermets can be changed over a wide range in dependencies from the chemical composition and sintering parameters. The most promising are cermets with a concentration of 9 wt.% of boron and 5–10 wt.% of Cu. They are made up of two phases: hard grains of iron copper boride, (FeCu) 2B (1700 HV0.1) as a reinforcement and a relatively softer and more plastic eutectic mixture Cu–B (α+β) (600–700 HV0.1) with a slight addition of iron as a matrix. The combination of these components produces good properties: high hardness, resistance to wear and acceptable ductility. An increase of copper portion facilitates diffusion processes which yields bigger boride fraction, smaller porosity and higher hardness. To obtain the best exploitation properties, like high hardness, and resistance to wear in elevated temperature it is necessary to minimise the eutectic mixture fraction. It depends on copper fraction and sintering parameters.