MACHINERY | SCREWS AND BARRELS
Right: Coperion developed its C-Rock material to extend wear protection and durability of its ZSK extruder barrels
days. Since this downtime cannot be made up, the output of the entire plant is reduced,” Diehl says. As a response to this challenge, C A Picard has developed a wear liner solution for highly wear- resistant protection zones that involves a coating – BX TapeTec – formulated to combine abrasion and corrosion resistance. The company says it employs ultra-strong carbides embedded in a ductile metal matrix and claims that these two compo- nents provide very good resistance to wear and corrosion. The company says it has developed a special coating process that allows an extremely high adhesion coating to be applied using a diffusion bond. It says that other coating methods typically generate a mechanical bond which has a higher risk of spalling. This spalling also often takes place as thick layers due to the residual stresses within the coating. According to C A Picard, while its BX TapeTec
coating has a layer thickness of 2–3 mm, no spalling occurs due to the highly adhesive nature of the bond and the particular conditions of the coating application process. To evaluate the capabilities of the coating, wear tests have been performed according to ASTM G65-04 and wear resistance compared to that of the company’s other standard materials (Figure 1). Abrasive wear has been shown to be considerably reduced even in comparison to highly wear-resistant BG steel, the company claims. Aside from the promising laboratory results, the
BX TapeTec coating has also performed very well in real-world projects with demanding wear challeng- es. C A Picard cites the example of a manufacturer
of engineering plastics with a highly abrasive application. It was using a 92 mm twin-screw extruder fitted with the company’s standard BG liner but had found this needed to be exchanged every three to four months, with the associated downtime-related costs that involved. The company opted to install the BX TapeTec liner material in 2018 — one of the first companies to do so — and reports that it has not yet required replacement. Another customer — Solvay Specialty Polymers — installed its first BX TapeTech liners in mid-2019 as part of a continuous improvement programme that included selection of improved corrosion and abrasion resistance alloys
for its barrels. An improvement
in the lifetime of the barrels has already been recorded compared to previous C A Picard alloys. According to C A Picard, its laboratory and
practical results show that the BX TapeTec coating is able to meet a wide range of performance requirements. It says that a benefit of the structure of the coating is that it allows for development of customised properties that can be adjusted to meet individual customer needs.
Figure 1. Wear resistance tests comparing CA Picard’s BX TapeTec against alternative barrel lliner alloys (ASTM G65-04) Source: C A Picard
56 COMPOUNDING WORLD | August 2021
Hard components Compounding machinery maker Coperion developed its C-Rock wear material to provide the highest wear protection and maximum durability for its ZSK extruder barrels. The company says the C-Rock wear material is characterised by a highly wear and corrosion-resistant matrix with specially selected hard material components. It is applied to product-contact parts of the ZSK extruder barrels with the result said to be a completely homogene- ous, closed surface screw channel with very good adhesion to the substrate material. According to Coperion, C-Rock provides the highest protection against abrasion and corrosion for the ZSK extruder barrels. It is said to improve productivity in difficult applications involving aggressive components and extends barrel life. C-Rock is said to be particularly effective in heavily stressed areas of the process section — such as the melting zone when mixing in abrasive particles, fibres or powders — and in the pressure build-up zone. Application of the C-Rock coating in these sections keeps barrel wear to a minimum and ultimately increases the efficiency of the entire extrusion line, the company says.
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IMAGE: COPERION
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