THE EFFECTS OF ANGLE OF IMPACT AND MATERIAL PROPERTIES ON THE EROSION FATES OF CERAMICS

One of the major areas of wear in the generation of power from coal occurs in the pneumatic transport of the pulverised fuel from the coal mills to the burners, This erosion of the pipes is vastly accelerated at the pipe bends, therefore the choice of lining material is extremely important. This paper addresses the problem through the systematic erosion testing, at different angles of impact, of fifteen erosion resistant materials, to determine their feasibility as lining materials, Other factors examined in this paper are the effects of target, erodent and system variables on erosion rates. Of the materials tested two were tungsten carbide cobalt cermets while the others were all ceramics most of them various grades of alumina. It is shown that the relative hardness of the target and erodent does not provide a clear prediction of erosion resistance. Microtoughness measured, using the indentation method, and modulus of rupture were found to give a good indication of erosion resistance with the materials tested. Threshold velocity and angle effects have also been observed and have been related to a change in the erosion mechanism. It has been found that at high angles of impact, 90 degrees and 60 degrees, material removal occurs through the formation of lateral fracture and the formation and removal of chips from the surface, While at the lower angles of impact, 45 degrees and 30 degrees, damage appears to be predominantly plastic in nature with damage accumulation necessary for the formation of lateral cracking.