Particle size effects on the elevated temperature erosion behaviour of Ni-Cr/WC MMC-based coatings

A. significant recent development in the study of solid particle erosion of materials at elevated temperatures has been the construction of materials performance maps. Such maps provide a means of minimizing the degradation of materials for a given set of conditions. For composite materials such as MMCs, they also enable optimization of materials parameters such as volume fraction and size of reinforcement. The object of this work was to investigate the effect of increasing erodent size on the wastage of Ni-Cr/WC MMC-based coatings at elevated temperatures. The performance was investigated at a range of temperatures and WC volume fractions using alumina particles as an erodent. The apparatus used was a laboratory-simulated fluidized bed, the environment was oxidizing, and the velocity ranged between 1 and 5 m s(-1). The results showed that erodent size had a significant effect on the transitions between the wastage regimes for such materials. Materials performance and selection maps were constructed showing the regions where the various volume fractions exhibited 'low' wastage. The potential of such maps to assist in the production of 'tailored' coatings, for specific applications at elevated temperatures, is addressed in this paper. (C) 1999 Elsevier Science S.A. All rights reserved