In the surface-critical stands in hot rolling mills, so-called indefinite-chill alloys are used as shell materials for the work rolls. The microstructure of these materials consists of cementite, graphite as well as different other carbides which are embedded in a martensitic/bainitic matrix. In the past ten years, indefinite-chill materials were intensively developed to meet the higher requirements in today's rolling mills. It was necessary to increase the fraction of wear-resistant carbides in the microstructure but still to maintain the very high surface quality of the rolls. Nowadays not only indefinite-chill or carbide-enhanced indefinite-chill can be counted to the state-of-the-art materials: the so-called graphitic HSS materials are regularly used in different hot rolling applications where highest wear resistance is needed.
To measure the increase of the wear resistance, a wear test rig was designed and developed which allows to test work roll materials under conditions which are very close to those in a rolling mill but still in laboratory scale. This paper shows the investigation results of four different indefinite-chill and graphitic HSS alloys with different carbide amounts and types. The strong influence of MC and M2C/M6C-carbides can be clearly seen but beside the carbides, also the other microstructural phases have an influence on the wear of the alloys. It could be confirmed that with higher fractions of hard carbides the wear on the tested materials decreased but the results also show clearly, that there has to be a correct balance between the different carbide types as well as the balance between the carbide, graphite and matrix fractions.