Investigation of Different Hard Coatings for Micromilling of Austenitic Stainless Steel

(Micro-)Machining of austenitic stainless steel is highly challenging due to the formation of build-up edges, adhesive tool wear and also the ability for work hardening, the low thermal conductivity, and the high toughness. Here, the application of tool coatings is a suitable method to extend tool life and to improve consequently the overall workpiece quality. Yet the qualification of different tool coatings for micromilling austenitic stainless steel has to be analysed.In this investigation micromilling experiments applying two fluted endmills having a diameter of d = 1 mm with different hard coatings were applied. The austenitic stainless steel X5CrNi18-10 (1.4301) served as the workpiece material. The tool coatings were CrN, TiN, AlCrN, AlTiN and TiAlN. Using a constant set of cutting parameters and the same basic tool geometry, the achievable performance of the different coatings was evaluated in terms of the process forces, the tool wear and the achievable surface quality. The application of a TiAlN and AlCrN coating generated very good results regarding the tool wear. Relating to the surface quality, the AlTiN coating provided the best results.