Bimetallic Coatings for Twin - Screw Extruder Barrels

Abstract

ABSTRACTIn this paper the development of novel wear/corrosion resistant coatings for twin screw extruders used in the food industry is discussed. The conventional materials used for extruder applications are reviewed and their limitations highlighted. The requirements for a new surface engineering philosophy are introduced and utilised to develop a new manufacturing system for the coating of extruder barrels. These coatings are based on Ni/Cr/B/Si/Fe alloys containing WC particulate. The processing route combines conventional PM technology with consolidation of the coating by hot isostatic pressing (HIPping). The HIP cycle is tailored to optimise the coating/substrate adhesion and the coating microstructure. Examples are given which illustrate the superior performance of these HIPped bimetallic coatings compared to conventional surface treatments.