Erosion in Hard Coatings in Pneumatic Conveying of Direct Reduced Iron Pellets

Abstract

Five samples of hard coatings (high chromium–high carbon) were separately tested for hot erosion resistance by multiple impacts of direct reduced iron (DRI) pellets in a hot erosion testing device. The volumetric wear and microscopic observations were used to evaluate the erosion mechanisms at different angles of impact. Microstructural parameters such as the partial area of the hard phase particles (carbides), the distance between the particles, and the mean free path were measured and correlated with the volume lost. The results of this work show a correlation between microstructural parameters, mostly the mean free path, with erosion resistance. Hot corrosion was inhibited by the use of a hydrogen inert atmosphere for the erosion testing. However, the hard coating samples were tested for hot corrosion in a reactor at 700°C. Metal dusting was present in stainless steel, but this kind of corrosion was not detected in the hard coatings. The results obtained here will help to evaluate the main mechanisms of pipe damage used in the high-temperature pneumatic transportation of DRI under industrial conditions.