Evaluation of the wear of plasma-nitrided and TiN-coated HSS drills using conventional and Micro-PIXE techniques

The machining performance of high-speed steel(HSS) twist drills that were p lasma-nitrided before applying physical vapor deposition (PVD) titanium nit ride (TiN) coating was evaluated and compared with that of representative, commercially TiN-coated drills. The performance criteria were (i) the tool lives from the flank wear land measurements of the drills, and (ii) the wea r features from micro particle-induced X-ray emission (Micro-PIXE), SEM and EDS examinations of two representative TiN-coated drills. The flank wear m easurements indicated that the pre-nitrided drills had longer tool life tha n the commercial drills. The wear features of the pre-nitrided drill indica ted that the TiN coating was subjected to progressive wear processes. On th e other hand, the wear patterns of the commercial drill revealed that the T iN coating experienced interfacial spalling. Plasma nitriding prior to the application of the TiN coating is one explanation for the improvement in th e machining performance of the pre-nitrided drills and for the observed dif ferences in the wear mechanisms of the two types of drills. (C) 2000 Elsevi er Science S.A. All rights reserved.