Novel high-performance CVD coatings for machining applications

Abstract

Investigations of hard and wear resistant materials have a long tradition to increase the performance and profitability of machining applications. The evolution started with WC-Co hardmetal alloys, which were produced by PM technology, followed by CVD coatings on hardmetal tools. The first CVD coatings applied were TiC, TiN and Al2O3. The properties of these coatings could be optimized by varying the crystal size, crystal orientation but also combination of the materials in multilayer systems. Nowadays, about 85% of all hardmetal tools are coated.During the last years, driven by PVD coatings showing good performance (e.g. TiAlN), the search for new CVD coatings was intensified. Medium temperature (MT) CVD processes for TiCN allowed the deposition of TiCN crystals with different composition side by side. Due to this microstructure the adhesion between single layers in new multilayer coatings like TiN/MT-TiCN/Al2O3/TiN could be increased. Novel (Ti,Al)N coatings were developed, showing a nanolamellae microstructure consisting of self-assembled (Ti,Al)N with different composition. For the future there is still plenty to investigate. The already existing coatings and coating systems have to be optimized for the various machining applications. To find new types of CVD coatings, we look for chemical reactions practicable for its use in CVD equipment.