Preparation and properties of nanoscale multilayered TiN/AlN coatings deposited by plasma enhanced chemical vapor deposition

Nanoscale multilayered TiN/AlN coatings were deposited on high-speed steel substrates by a plasma enhanced chemical vapor deposition process. Multilayered TiN/AlN was prepared by the alternate deposition of TiN and AlN, using an automatically controlled valve system. TiCl4 and AlCl3 were used as the precursors for TiN and AlN, respectively. The structure and micro-hardness of the coatings before and after heat treatment were investigated. The coatings showed a random crystal orientation with broad X-ray diffraction peaks and had a very dense and fine-grained structure. The hardness of the coatings was greater than 5000 kgf/mm2, when the layer period was 5 nm. The hardness was maintained at over 4000 kgf/mm2 up to an annealing temperature of 900 °C then decreased with increasing annealing temperature ⩾1000 °C.