A nanoindentation based determination of internal stress alterations in PVD films and their cemented carbides substrates induced by recoating procedures and their effect on the cutting performance

Through the reconditioning of worn coated cutting tools by means of appropriate de-coating, micro-blasting and physical vapour deposition (PVD) recoating procedures, a production cost decreasing is intended. However, the cutting performance of recoated tools may be impaired compared to the corresponding one of new tools, due to the fact that during the reconditioning processes strength properties modifications in the substrates are induced, resulting in a potential wear behaviour deterioration. In this way, the cutting performance reliability and in general the tool cost management could be unfavourably affected. In the investigations described, a procedure based on nanoindentations and a finite elements method (FEM) supported evaluation of the corresponding measurement results is applied. This method enables an accurate determination of coatings and cemented carbides inserts mechanical surface strength properties and, moreover, of related internal stress alterations at every stage of reconditioning procedures. The occurring surface stress modifications in cemented carbides inserts during reconditioning procedures might affect the tool cutting performance. Investigations in milling and gear hobbing showed that the inferiority of the tool wear behaviour when using reconditioning cemented carbides tools, could be drastically reduced. The methodology introduced, contributes to the achievement of this target, since it facilitates the accurate assessment of the reconditioning procedures effect on the tool mechanical properties.