American patents

Abstract

An investigation has been carried out into the manufacture and field trial of alloy white iron beater plates used to process coal in a KSG coal pulveriser mill. The components were made by the cast bonding process, which involves casting a wear layer onto a steel substrate to form a bimetallic composite product. Four alloy white irons, containing primary and/or eutectic carbide volume fractions ranging from nominally 10 to 40%, were used as the cast overlay in the manufacture of the beater plates. Two replicates of each alloy composition were tested in a mill along with two standard austenitic manganese steel plates. All beater plates completed 3275 h of operation, with the best-performing alloys receiving an additional 3471 h of service in a second campaign. The results showed that increasing carbide volume fraction decreased the wear rate most markedly at sites of low-angle erosion, and that it had a smaller influence at higher angles of abrasive particle attack. Subsequent scanning electron microscopy examination of worn components revealed that the primary mode of material loss at the lower carbide volume fractions was microspalling, with sub-surface fractures occurring within the carbide particles and along carbide-matrix interfaces. Surface microgrooves were more evident in the alloy white iron beater plates with higher carbide volume fractions.