Micro-milling machinability of pure molybdenum

As a result of the miniaturization of machined shapes, the conventional micro-milling technology has been widely used in many industrial areas. However, the machining of some types of materials proved to be very difficult. One of the hard-to-machine materials is also pure molybdenum, which, thanks to its high melting temperature, is used, besides others, in the energy industry and for physical applications. To ensure proper functionality of the manufactured parts, it is essential that they are machined without defects and with the required surface quality. The aim of this study was to find an optimal tool with a diameter of 0.8 mm and to set the machine parameters for machining of pure molybdenum with the highest quality of the surface layer possible without any defects. For this purpose, 26-round design of experiment (DoE) was carried out, in which the parameters, like cutting speed, feed, and coating (yes/no) were systematically changed. The machined samples were evaluated for topography using a 3D profilometer; their morphology and burrs were studied using an electron microscope, and the microscopic implications on the microstructure of the subsurface layer were studied on the produced lamellae using transmission electron microscope (TEM). In addition, the tool wear curve was examined and evaluated. In this study, an optimal setup of machining parameters for pure molybdenum machining (cutting speed = 80 m/min, feed = 0.002 mm/tooth, non-coated tool) was found with which high-quality and defect-free surfaces can be machined.