Wear resistance and cutting performance of high-speed steel ball nose end mills related to the initial state of tool surface

The wear resistance and cutting performance of uncoated and coated high-speed steel ball nose end mills were investigated. A fine-scale multi-component B–C–N diffusion coating was produced on AISI M35 steel substrate at 580 °C for 1 h. The surface and the cross-sections of the samples were subjected to detailed characterisation focusing on a surface condition of the uncoated and coated tools. It was shown that after grinding operation certain surface defects are observed in the steel matrix as well as in the exposed carbides in the case of the uncoated tool. In contrast, the microstructure of the surface of the coated tool appeared to be more uniform and without any visual surface defects. In general, the results established that there are two aspects to the wear behaviour of the coating, its main ability to resist plastic deformation during abrasive wear, which was in line with the results of the nanoindentation test, and secondly to recovering the surface defects of the ground surface thus enhancing the surface integrity. As a consequence, the lifetime of the coated tool was 2.5 times greater. [Display omitted] •After grinding, surface defects were observed in HSS substrate and exposed carbides.•Coating led to recovering the surface defects formed during grinding operation.•Cutting tests of uncoated and coated HSS ball nose end mills were carried out.•Coating reduced significantly intensity of plastic deformation during abrasive wear.•Lifetime of coated mill was 2.5 times longer compared with that of the uncoated tool.