Properties and Applications of Nano-cBN Coatings

One goal in the field of c-BN deposition is a coating which can be used for machining of iron-based materials. Such coatings offer the possibility to use a superhard material instead of the conventional carbide and oxide layers. 

Matsumoto and co-workers showed that the deposition of thick nano-cBN layers is possible and the adhesion on Si substrates is of acceptable quality [230]. The one major question is whether this process is also suitable for hardmetal (WC-Co) substrates or not, and whether there might be any problems with the Co binder phase and the BF3 in the gas phase  

The stress in c-BN layers caused by the high energetic ions is a problem, because many of the nano-cBN coatings delaminate during or immediately after deposition. Several investigations have showed ways to reduce the stress in the layers (e.g. buffer layers [205, 217, 236], regulation of the ion energy [207], or ion-induced stress relaxation [206]). 

The outlook for industrial applications of nano-cBN coatings looks quite good, but some problems with the deposition process and the substrate materials still have to be solved. 

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