(Image Courtesy of Sandvik Coromant)
In ferrous machining applications, it is common for polycrystalline cubic boron nitride (PCBN) tools have a tendency to chip on the micron scale, particularly during processes such as the turning of hardened steel. A "chip breaker" gives the added benefit of controlling and guiding the flow and breaks of chips, while lessening contract stress to avoid white film build up. Today, applying cubic boron nitride (cBN, which is also the second-hardest ceramics material, next to diamonds) is the only practical way to create chip breakers of varying geometries, even though several other options have been pursued. An article by ceramicindustry.com discusses major advancements in this aspect of ceramics engineering, drew the following conclusion:
"Cubic boron nitride particle composite coatings can be readily applied to cutting inserts with chip breakers through the use of patented coating technology. In straight turning of AISI 4340 hardened steel, the coated chip breakers produced a tool life equivalent to PCBN-tipped flat inserts under identical conditions. The machined surface with chip breakers has a surface finish approaching 0.8 µm without the formation of a white layer. Thus, the ceramic coating-coated inserts can be an important complement to PCBN ceramics, offering extended tool life, improved machined surfaces and better economics."
The article goes on to state that the cost of this coating is comparable to other options for chip breakers that currently exist in the industry, while adding the benefit of being able to be tailored to fit more specific geometries. While the price-point alone should be enough to sway most ceramics manufacturers, the efficiency of the material should also be taken into consideration, as "with its combination of hardness and toughness, the composite coating adheres well to the carbide substrate and does not show particle pull-out or coating delamination at a critical loading of 10 kg in scratch testing." With a larger range of applications and a cost-effective price, it is likely that this new generation of chip breaker will become a major part of ceramics engineering in years to come.
To read more about this new and exciting technology, follow the link:
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