Deposition of Hard Films on Hot-Work-Steel Dies for Aluminum Extrusion
K. B. Müller, Forschungszentrum Strangpressen, Technische Universität Berlin (Technical University Berlin)
Track: DIE DESIGN AND TECHNOLOGY - Surface Treatments and Materials
ABSTRACT --- In the extrusion process of aluminum alloys at elevated temperature,
the dies are used under very severe thermal and mechanical stresses.
Furthermore, sliding friction and adhesive wear occur in the interaction zone
between extrusion die and extrusion product. To improve the die performance and
the quality of aluminum products, a duplex process combining a plasma nitriding
(PN) pretreatment and a plasma-assisted chemical vapor deposition (PACVD) or
plasma-assisted physical vapor deposition (PAPVD) was applied on the extrusion
dies, which are made of the hot-work steel X38CrMoV5-1. The duplex layers are
produced at a temperature of 530°C. The effects of process parameters during
plasma nitriding, such as duty cycle, nitrogen concentration in process gas, and
nitriding time, are investigated. The optimized modification of the die surface has
been achieved. The duplex layers (TiBN-, CrN- and W-C: H-films on the
plasmanitrided films) have a higher macrohardness (HV9.5) and critical load in
comparison with conventional films without the plasma nitriding treatment. The
performance of the coated dies are examined by means of direct extrusion trials.
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