Development of high-performance extrusion barrels with innovative gradient coatings

Barrels for polymer extruders have to sustain severe service conditions. In the inner volume of a barrel for polymer processing, high temperature, high pressure and corrosive media lead to mixed forms of abrasive, adhesive wear and corrosion. Moreover, during the extrusion process, the conditions vary along the barrel length from sections where mainly abrasion occurs, to sections where corrosion dominates. To extend service life, the barrels are usually coated with hardfacing alloys of thickness up to the millimetre scale by spin casting, PTA or laser cladding. In the present contribution, an overview is given about the activities carried out in the frame of the Debacoat project funded by the EU. Issues are mainly addressed toward the development of new hardfacing alloy compositions, on laser cladding of internal surfaces of the barrels by mini laser heads and on the deposition of WC reinforced Ni-Cr alloys by laser.