Effect of plasma nitriding potential on tribological behaviour of AISI D2 cold-worked tool steel

• The effect of plasma nitriding atmosphere on the wear of D2 steel is evaluated.
• Finely dispersed nitrides-containing nitrided layers reach a hardness of 1350 HV.
• Layers without a compound layer and grain boundary nitrides reach higher wear resistance.
• The wear mechanism of untreated or nitrided steel is dominated by three-body abrasion rolling.

The effect of the nitrogen potential on the micro-abrasive wear resistance of AISI D2 plasma nitrided tool steel was evaluated. Plasma nitriding experiments were conducted in a pulsed plasma reactor using different nitrogen potentials. The results indicate that a nitrided layer, with finely dispersed nitrides, can be formed when shorter nitriding times and higher nitrogen potentials were used. Although the thickness of this layer is small, its wear resistance is higher than that observed at longer nitriding times. Increasing the nitriding time resulted in the formation of thicker layers, albeit with grain boundary nitrides, which are deleterious to wear resistance. For untreated material, three-body abrasive wear rolling was the dominant mechanism, and for nitrided material, the mechanism transition was not clearly observed in spite of its better wear resistance.