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Licensed Unlicensed Requires Authentication Published by De Gruyter February 23, 2021

Investigation of wear on the upper edges of webs of thin-film coated single-screw extruders processing pure polymers

Torben Buttler, Jens Hamje, Rolf Reiter and Volker Wesling
From the journal Materials Testing

Abstract

During polymer extrusion there are a variety of situations in which the screwthread of the extrusion screw has an unlubricated metal-to-metal contact with the barrel wall. At the same time the screw coating is subjected to the highest loads. The combination of a secondary hardening cold work steel 1.2379 and a chromium nitride coating deposited by ARC-PVD, which is frequently used in polymer processing, is characterized and investigated. The characterization is done by metallographic examination, SEM and CLSM. The tests were performed on a pin-on-disk and a pin-roll test rig. Different roughness levels were tested on the pin-on-disk test, where massive differences in wear behavior were found. A hybrid surface structure is proposed to optimize the tribosystem. On the pin-on-disk test stand, rollers made of the same material pairing were tested. The test speed was varied to highlight differences and similarities between the tribological systems. A wear minimization of 50 % was achieved and the similarities between the tribological systems were highlighted. In addition, the investigations led to the development of a new model thesis which provides a reason for the development of stippling on the screw when processing polycarbonate.


Torben Buttler Institute of Welding and Machining Agricolastrasse 2 38678 Clausthal-Zellerfeld

Acknowledgement

This work was carried out by the Association of Industrial Research Associations “Otto von Guericke” e.V. (AiF) within the scope of the project “Belagbildung unter Betriebsbeanspruchung” (20333 N/3). Furthermore Dr. Wegewitz and Dr. Gustus (IEPT – Institute of Energy Research and Physical Technologies – TU Clausthal) are thanked for the production of the SEM images.

Nomenclature

CLSM

confocal laser scanning microscopy

FIB

focused ion beam

SiO2

silicon dioxide

CrN

chromium nitride

PC

polycarbonate

Ra

arithmetic average roughness

Rz

averaged roughness depth

„xxx“

grinding papers grit size

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Published Online: 2021-02-23

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