Abstract: SEM, EDX, Rockwell hardness tester, analytical balance and XRD are used to study the evolution of the microstructure and wear mechanism of the worn surface of a WC-Co based alloy used for guider roller in the process of steel-bar rolling. After the alloy has been used for rolling 2 000 t of 45 steel at about 1 000 ℃, the density maintains almost the same while the hardness decreases from 56 HRC to 49 HRC. Further investigation shows that some big crystals dynamically recrystallized and nano-grains with the size of about 200 nm formed in these big ones in the process of steel rolling, which contributes to the decreasing of hardness of the alloy. The results also show that the main wearing mechanism of the alloy includes plastic shearing and ploughing. Additionally, abrasion and fatigue also contribute to the wearing of the alloy. At last, models for the explaination of fatigue and ploughing wearing are presented.

Key words: Guide roller, Nano-grains, WC-Co based alloy, Wearing mechanism