The use of modified polymers and elastomers for improving mechanical and chemical properties also leads to negative side‑effects that require correction.

Abrasion, corrosive degradation products, cavitation, adhesive interactions and erosion are all wear mechanisms induced by additives in the polymers, with the consequence of premature tool failure during the production process. Removal and servicing of tools, and the downtimes involved, result in a significant increase in production costs. Sulzer Metaplas offers an effective means of counteracting these wear phenomena, in the form of a duplex treatment consisting of plasma-nitriding combined with the respective PVD hardcoating process. Enormous potentials for savings and for enhancement of productivity and profitability vis-à-vis non-coated tools are powerful arguments in favor of the use of coated tool elements.

Plasma-nitriding applied prior to PVD coating is recommendable in order to counteract the tribological attack to which surfaces are exposed. Plasma-nitriding is a classical surface treatment, in which surface hardness is increased by means of diffusion of nitrogen into the surface in a glow-discharge plasma. The plasma-nitrided layer plays a supporting role for the subsequent PVD hard coating, guaranteeing its optimum wear-resistance. Plasma-nitriding ensures that the surfaces of plastificators possess the necessary hardness and that glass fibers, for example, are not able to penetrate the thin coatings.

Metaplas hard coatings are generated by physical deposition from the gas phase. In this process, atomic forces assure excellent bonding between the coating and the substrate. The classical Metaplas TiN, CrN, CrN multi-layer, CrN-mod and dry lubricating W-C:H PVD hard coatings, in particular, have proven their wear-protection capabilities in the plastics- and elastomers-processing industries. The broad range of available coating variants makes it possible to meet the different requirements of polymer-processing, with coating possible from temperatures as low as 180° C. The combination of plasma-nitriding and PVD coating also permits processing of heat-treating steels and less hardenable hot-work tool steels. The beneficial mechanical properties of the center of the material, such as toughness and insensitivity to cracking, remain unchanged in this process.

The selection of the individual coating systems is highly orientated around the polymers and elastomers to be processed and the individual parameters of the particular process. A coating specifically tailored to the particular application, combined with correct material selection and plasma-nitriding, when appropriate, permits maximum optimization of service life and thus, overall process cost-efficiency. The enormous potential for enhancement of service-lives makes it essential that coatings have to be considered in the tool design phase. The positive effects achieved here also produce decisive advantages for other operational sectors: improved production-dependability enhances delivery-reliability and the entire company's competitiveness.