Abrasion-induced microstructural changes during low stress abrasion of a plain carbon (0.5% C) steel

Abstract

A plain carbon (0.5% C) steel was subjected to various heat treatment cycles to produce a variety of microstructures. Low stress abrasion tests were conducted using an ASTM standard rubber wheel abrasion test apparatus. Crushed silica sand particles were used as the abrasive medium. The wear loss decreased progressively with the number of test intervals until a steady state was reached. The steady state abrasion resistance was found to increase linearly with bulk hardness up to about 350 HV beyond which there was a marginal increase. Abrasion-induced changes were studied via metallographic examinations of transverse sections and hardness vs. depth (below the abraded surface) profiles. Abraded surfaces and wear debris were examined in a scanning electron microscope equipped with a wavelength-dispersive X-ray spectroscope. The hardened steel showed a large number of continuous and parallel grooves, while the annealed specimen revealed a considerable amount of micropitting in addition to the grooves. Wear debris from the annealed specimen was mainly of the flake type, while long micromachining chips of the “card-deck” type were observed in the case of the hardened steel. The results of this study revealed that the material removal mechanisms during abrasion of steels are controlled by the properties of a layer beneath the abraded surface. The properties of this layer are in turn governed by the bulk microstructure.