Industrial applications of metal nitrides

   Nitrides of the d-block metals are hard, are resistant to wear and chemical attack including oxidation, and have very high melting points. These properties render nitrides such as TiN, ZrN and HfN invaluable for protecting high-speed cutting tools. The applied coatings are extremely thin  (typically ≤ 10 µm), but nonetheless significantly prolong the lifetimes of tools that operate under the toughest of work conditions. Nitride coatings can be applied using the technique of chemical vapour deposition or by forming a surface layer of  Fe₃N or Fe₄ N by reacting the prefabricated steel tool with N₂. Layers of TiN, ZrN, HfN or TaN are applied as diffusion barriers in semiconducting devices. The barrier layer (≈100nm thick) is fabricated between the semiconducting material (e.g. GaAs or Si) and the protective metallic (e.g. Au or Ni) coating, and prevents diffusion of metal atoms into the GaAs or Si device