Erosion of a High Carbon Steel in Coal and Bottom Ash Slurries

This paper discusses the observations made during erosive wear testing of a high-carbon steel (0.65% C) in coal and bottom-ash slurries. The slurry was made by separately dispersing 30% coal and bottom ash (collected from a thermal power plant) in tap water. The tests were performed using a sample rotation method in the slurry at a fixed linear velocity of 5 m/s for different traversal distances at room temperature. To see the influence of microstructural features on slurry wear response, the steel was subjected to hardening and annealing heat treatments. Test results indicate that material loss of the specimens increased with traversal distance in all cases. Further, the hardened steel showed a lower rate of material loss when compared with steel in an annealed condition in either of the test environments. Moreover, irrespective of heat-treatment conditions, the samples revealed significantly higher material loss when tested in the bottom-ash slurry than in the coal slurry. The higher rate of material removal in the case of the former was attributed to the more efficient transfer of the kinetic energy of the moving (hard) bottom-ash particles to the specimen surface than in the case of the softer coal particles. Fracture of coal particles as a result of impact during the course of slurry erosion further supported the view. Results have been explained on the basis of the characteristics of the affected surfaces and changes in the morphology of the erodent particles after the test