Longer Life Span

A combination of plasma nitriding and a hard-facing layer effectively extend the lifespan of tools that are subjected to high wear. The increased production dependability enhances delivery reliability and the competitiveness of the entire enterprise.

Abrasion, corrosion, cavitation, adhesion, and erosion are all wear mechanisms induced by additives in polymers; these factors often lead to premature tool failure during the production process. The 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 hard-coating process (Figures 1 & 2). The enormous potential savings, productivity and profitability enhancements over non-coated tools are powerful arguments in favor of the use of coated tool elements.

Combined treatment
Plasma nitriding applied prior to physical vapor deposition (PVD) coating is recommended in order to counteract the tribological attack to which surfaces are exposed (Figure 3).

Plasma nitriding is a classical surface treatment, in which surface hardness is increased by means of the diffusion of nitrogen into the surface using glowdischarge 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 ensure 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 (Figures 4 & 5).

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 quenched and annealed steels and less hardenable hotwork tool steels. The beneficial mechanical properties of the bulk of the material, such as toughness and insensitivity to cracking, remain unchanged in this process.

Tailored coatings
The selection of the individual coating systems is highly oriented around the polymers and elastomers to be processed and around 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 significant extension of service lives and, thus, of overall process cost efficiency. The enormous potential service life for enhancement makes it essential that coatings 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.

Fromme, Martin. "Longer Life Span." Sulzer Tehcnical Review, Jan. 2010: 26-27.

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