Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Surface hardening for aluminium moulds: optimised coating process for surface hardening of aluminium alloys

An optimised coating process for surface hardening of aluminium alloys was developed with the following parameters: thickness: 100µm (partline), 10 µm (cavity), hardness: < 2500 HV (partline), 2500 HV (cavity). Surface treatments on the aluminium moulds have to be deposited below 150 °C in order to preserve the mechanical properties of the alloy. Those surface treatments provide:
- a surface hardening that protect the mould against wear occurring on the movable parts during the demoulding operations;
- anti-sticking properties that will allow a better demoulding of the moulded part.

Two types of surface treatments were considered: conventional treatments (electroless Ni for example), and PVD / PACVD treatment that have been developed to be specifically applied on aluminium alloys.

Achieved results:
- A cleaning procedure, specifically designed for aluminium, has been defined. This procedure allows a cleaning prior the PVD / PACVD surface treatment that not corrode the aluminium surface and offer a good degreasing before beginning the vacuum treatment;
- Three PVD / PACVD coatings have been developed. Cr2N, CrN and DLC have been deposited with process temperature below 150 °C. The hardness is around 2 000 kg / mm2 for the two chromium nitride coatings and more than 2 500 kg / mm2 for the DLC coating. The thickness is comprised between 1 and 3 µm depending on the coating. A combination of DLC deposited on chromium nitride (in the same batch) has also been developed to improve the load bearing capacity of DLC. The new PVD / PACVD processes can be applied to all kind of aluminium alloys parts and can also concern applications different from moulding.

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