To the Question of the Mechanism of the Effect of Coating on the Durability of Tools from PCBN

The paper discusses the results of the tool-life tests of PCBN cutting tool with PVD coating and the mechanism which could be accounted for declining of its wear rate. The results of research showed that in condition of finishing of hardened steel (52–54 HRC), PCBN with (TiAlSiY)N/CrN PVD coating demonstrated significantly lower wear rate parameter in comparison with a standard composite. The maximum VB value of the modified tool is 3.2 times smaller after 24 min of the total cutting time. The evaluation of morphology of the worn areas of the tools had been done. No significant differences of crater form and depth on the rake face of coated and non coated tools were found. At the same time the evidences of intensive plastic deformation occurring on the clearance face of the tool with protective coating caused by wear land topography peculiarities were found. Plastic flow-zone formed at this area can significantly reduce the abrasive effect on the tool surface and thus increase the overall tool-life.