Nanolock: The world’s first nanocrystalline bonding layer

High-speed cutting places enormous demands on machines and tools. Therefore, multilayer coatings have proven their worth in protecting tools from wear. Depending on how they are to be used, they are either especially hard or especially tough. With its innovative Nanolock technology, Boehlerit has now succeeded in combining both properties in one cutting material for the first time. The world’s first nanocrystalline bonding layer is the basis for this, considerably improving the adhesion between the cutting body and cutting layer.

Nanolock: traditional titanium carbonitride in a new form

Titanium carbonitride coatings are generally used as a protective layer to prevent wear in carbide indexable inserts and tools. Over 90 percent of all CVD-coated indexable inserts in multilayer designs contain at least one TiCN layer. It is usually used to bond a ceramic layer such as aluminium oxide to the tool or cutting edge. In spite of extensive experience in the various procedures, a central problem has remained unsolved until now. Although multilayer coatings can protect tools from high thermal and mechanical stresses during machining, the relatively thick CVD layers in comparison with PVD coatings lead to high turning speeds which cause the individual layers to literally fly apart once a certain speed is reached. The functional properties particularly depend on the microstructure, size and orientation of the crystals in the coating.

Greater wear-resistance thanks to the nanocrystalline structure

Because of these properties, a major development goal is to reduce the size of the coating’s particles, thereby increasing the mechanical characteristics considerably. It has been demonstrated, for example, that a crystallite size of approx. 50 to 300 nanometres with equiaxial crystal growth considerably increases TiCN wear-resistance. This is precisely what Boehlerit developers have achieved with the new Nanolock layer, as the new layer has a roughly 3-times finer crystallite size of only around 25 nanometres. Furthermore, investigations with an electron microscope have shown that the new surface has a “composite character”, i.e. two different crystal types are present next to each other at the same time. The Nanolock coating also has an ultra-fine, needle-like surface that enormously improves the adhesion of the next layer. Thus, Boehlerit has succeeded in achieving what had appeared impossible to date - to mix carbon and nitrogen elements in the titanium carbonitride layer.

Numerous cutting trials have shown that the Nanolock layer is extremely hard as a result and only marginally affected by abrasion. Instead, the high temperatures tend to cause typical wear on flanks through plastic deformation at the cutting edges. Oxide layers such as aluminium oxide, which are used as a thermal “protective shield”, ensure effective protection here. Thanks to the new Nanolock layer, Boehlerit can optimally combine the abrasion-resistance properties of the titanium carbonitride with the heat-resistance properties of the aluminium oxide. Users benefit from significantly higher cutting speeds and above-average tool life.