The development of new wear/corrosion resistant coatings for extruder barrel applications in the food and plastics processing industry is reviewed and the surface engineering philosophy discussed in conjunction with detailed analysis of the degradation mechanisms. The new coating approach combines conventional powder metallurgy technology with a novel method of structuring the coating both laterally and in a direction normal to the surface. In this technique the powders are consolidated by hot isostatic pressing to optimise the structure and interfacial adhesion.
