Tribological behavior of variously surface-treated X48CrMoV8-1-1 tool steel for application on chipping knives in wood-chipping machines

The aim of this work was to assess the suitability of selected methods of surface treatment on X48CrMoV8-1-1 tool steel for application on chipping knives in wood-chipping machines. Three material surface conditions of X48CrMoV8-1-1 tool steel were evaluated for their tribological scratching behavior. The first surface condition was related to the conventionally machined chipping knife from the manufacturer without surface treatment. The second condition involved plasma nitriding treatment, and the third was a PVD-coated surface with “CROSAL ® Plus” (AlCrN based) coating. Several complementary analyses were carried out, namely microstructural observations, nano-indentation measurements, and tribological scratch tests. From the scratch tests, friction coefficients depending on applied load were determined. The best nano-indentation results were obtained for the PVD-coated surface, namely 23.7 ± 1.6 GPa for nanohardness and 270.3 ± 19.0 GPa for elasticity modulus. The best results of tribological and scratching behavior were obtained for the plasma-nitrided surface, namely 0.34 ± 0.21 for coefficient of friction and 1.88 × 10-6 mm3/N.m for specific wear rate. Based on the obtained results of laboratory tests, it can be concluded that the plasma-nitrided surface of X48CrMoV8-1-1 tool steel can ensure its better tribological performance compared to other investigated material conditions.