Duplex surface treatment of the Nb-alloyed PM tool steel

In this work we studied the influence of the nitriding atmosphere composition on hardness, microstructure, phase composition and wear resistance of duplex treated cold work PM tool steel alloyed with niobium (2.6 wt.%). Pulsed-plasma nitriding was carried out at 500 °C for 180 min, the atmosphere composition was N2:H2 = 1:3 and 1:6. After nitriding, the material was PVD coated (magnetron sputtering) with TiAlN layer. The PVD coat was also applied upon a non-nitrided material. We found out that when both nitriding conditions were applied the wear resistance was significantly higher than the PVD — only coated material. The best wear resistance was achieved when the TiAlN coating was supported by a layer applied by nitriding in a lower-nitrogen atmosphere (N2:H2 = 1:6). These conditions prevented formation of an undesirable compound layer in the nitrided layer.