9.1 Introduction

The productivity of the manufacturing industries has constantly improved during the 20 ^th century. This is the result of the spectacular increase in the speed of stock removal by cutting tools, faster penetration of drills (petroleum, mines, public works), as well as the considerable improvement in the resistance to wear, fatigue and corrosion of the components of mechanical systems.

These achievements are mainly linked to the discovery, study and development of hard and superhard materials such as ceramics and cermets.

The term "cermet" denotes a composite material containing at least one ceramic phase and one metallic phase. Used here in the broader sense of the term, ceramic designates composites with highly localized bond strengths, covering not merely oxides (Al ₂O ₃, Cr ₂O ₃, ZrO ₂, UO ₂, etc.), but also carbides (WC, TiC, TaC, Cr ₃C ₂, etc.), nitrides (TiN, etc.), borides (TiB ₂, CrB ₂, etc.) of refractory transition metals and their combinations or solid solutions (oxycarbides, oxynitrides, carbonitrides, etc.), as well as some elements and covalent composites (diamond, BN, B ₄C, SiC, Si ₃N ₄, AlN, etc.). The ceramic particles have an average grain size between 0.1 and 100 ?m and their volumetric content in cermet is more than 15%. The metallic binder consists of one of the transition metals (mainly Co, Ni, Fe) or their alloys (Ni/Co, Ni/Cr, Ni/Mo, Fe/Cr, etc.).

Carbide-based cermets constitute the majority of...