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  • Film thickness effect on me...
    Skordaris, G.; Bouzakis, K.-D.; Kotsanis, T.; Charalampous, P.; Bouzakis, E.; Lemmer, O.; Bolz, S.

    Surface & coatings technology, 12/2016, Volume: 307
    Journal Article

    The paper aims at clarifying whether thick HPPMS (High Power Pulsed Magnetron Sputtering) PVD coatings can be used more effectively in cutting processes compared to thin ones. In this context, nano-structured multilayer HPPMS PVD coatings with diverse thickness were deposited on cemented carbide inserts of the same specifications. The deposition of multilayer PVD coatings instead of mono-layer ones on cemented carbide tools contributes to a significant improvement of the coated tool life due to their capability to prevent the crack propagation. The coating's mechanical properties and their gradation versus the film thickness were determined by analytical results' evaluation of nanoindentations on annealed coated specimens. The films' brittleness was assessed by nano-impact tests. The strain rate-dependent fatigue endurance of the applied coatings was determined by means of impact tests with modulated force signals, resembling the developed ones during milling. The coated inserts were used in milling hardened steel. A Finite Elements Method (FEM) simulation of the contact between the coated tool and the workpiece provided information for elucidating the effect of the film thickness on the tool wear evolution. These investigations revealed that via increasing the film thickness the tool life is prolonged almost proportionally with the coating thickness augmentation, thus compensating for their higher cost compared to thin coatings. Display omitted •Cutting tools were coated with nano-structured multilayer films of diverse thickness.•The coating's mechanical properties were determined via innovative test methods.•The film mechanical properties deteriorate when increasing the coating thickness.•The raise in coating thickness enlarges almost proportionally the coated tool life.•The prolonged tool life compensates for the higher cost of a thick coating.