Improvement of Wear Resistance of DC11 Tool Steel by Nitrocarburizing

Abstract

In the present investigation, the influence of nitrocarburizing holding time on the wear behavior of DC11 tool steel is reported. DC11 tool steel was nitrocarburized at 570℃ for varying durations of 1, 3, and 5 hours. The microstructures and hardness of the nitrocarburized coatings were then analyzed. Wear behavior was examined on a block-on-ring wear tester under unlubricated conditions. Sliding distance was varied from 188 to 1880 m. The results show that surface compound layers consisted mainly of e-phase (Fe3N) together with γ'-phase (Fe4N). The nitrocarburizing treatment not only increases the surface hardness but also improves the wear resistance of DC11 tool steel. Wear of the untreated specimen is severe and is characterized by strong adhesion, thus showing a rather unstable friction coefficient, while also exhibiting the highest dry-sliding wear rate. On the other hand, all the nitrocarburized specimens exhibit a relatively lower- and stable friction coefficient. Furthermore, friction coefficients of the nitrocarburized specimens do not change significantly with holding time and wear rate varies as a function of the sliding distance due to the presence of different wear mechanisms. For short sliding distances, wear rates depend on three mechanisms: plastic deformation, abrasive wear, and spalling of the compound layer, whereas for larger sliding distances the mechanisms controlling wear rate are abrasive wear and friction polish.