Evaluating the potential of a nano-layered CrAlYN/CrN HIPIMS coating to improve the hot forging die life of plasma nitrided H13 steel

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During a hot forging production run, the dies are subjected to cyclical mechanical and thermal stresses. Typically, these will cause the surface condition to deteriorate according to an interplay of damage modes until such point that production must be halted for a die changeover. This invariably has a significant cost impact in terms of time, material, and labour. In industry, the most widely used method of improving the surface durability of hot work tool steel forging dies is nitriding. To the author’s knowledge, this is the first time that a HIPIMS coating has been tested for this purpose. The experiments were carried out model dies fabricated from H13 treated by plasma nitriding and duplex treated by plasma nitriding followed by coating using CrAlYN/CrN HIPIMS coating.

The Superlattice structured CrAlYN/CrN with by layer thickness of Δ=3nm was deposited in industrial size Hauzer 1000-4 system enabled with HIPIMS technology at the national HIPIMS Technology Centre UK. Due to the special HIPIMS surface pre-treatment the adhesion of the coating to the plasma untraded surface was excellent of class 1 determined in a Daimler Benz indentation test In high temperature, T= 650 °C pin-on-disc tests using specially prepared counterpart of Inconel 718 the coating showed low coefficient of friction of µ= 0.42 and exceptionally low wear coefficient of KC = 6.04 x 10-13 m3N-1m-1.

260 Inconel 718 billets preheated to 1000 °C were forged onto each in an industrial-scale screw press. The post-forging dies were analysed with a GOM 3d coordinate measuring system, 3d optical profilometry, and SEM with EPMA. Die conditions during the run were inferred from GOM analysis of every fiftieth billet. In terms of local volume loss, the duplex-treated die after 100 forgings was superior to the plasma nitrided die after 260. Moreover, such was the loss from the front edge of the nitrided die, that the rate plateaued after 200 forgings. In contrast, with the HIPIMS coating loss in this region was barely measurable. The plasma nitrided die underwent surface texture, (surface wear) parameter increases of up to 53 times. The highest increase measured for the duplex-treated surface was only by a factor of 3. In a further metric of performance, thermomechanical fatigue cracks were evident on the plasma nitrided die. No such cracks were found on the duplex-treated dies.
Original languageEnglish
Publication statusPublished - 14 Jun 2023
EventInternational Conference on HIPIMS - Venlo, Netherlands
Duration: 12 Jun 202315 Jun 2023
Conference number: 13


ConferenceInternational Conference on HIPIMS


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