New wear-resistant materials for mining applications

Abstract

Economic and political driving forces are leading to an ambitious search for substitutes for fused
tungsten carbide (FTC) in ultra-high wear-resistant metal matrix composites (MMC), which are
used for mining applications. In the presented paper, possible substitutes such as alumina (Al₂O₃),
zirconia (ZrO₂) and silicon carbide (SiC) are discussed. To enhance the wettability of oxides (e. g.
Al₂O₃, ZrO₂) by Fe-base melts or to counteract strong dissolution of metastable covalent bonded
hard-particles (e.g. SiC) it is proposed to coat the particles with a thin titanium nitride (TiN) layer by
means of chemical vapor deposition (CVD). For this reason a CVD-apparatus for particle coating
was constructed and is shown in this paper. In addition, it is demonstrated that such a TiN coating
on the oxide particles can increase the wettability and therefore improve the embedding behavior
of the particles into a Fe-base matrix. In addition, it is shown that TiN coatings on covalent bonded
hard-particle SiC can be used as a diffusion barrier coating, thus counteracting a dissolution of the
hard-particles during processing by sintering techniques. However, due to the difference in linear
thermal expansion coefficients the coating tends to delaminate, partially.