H13 steel was nitrided using a plasma surface alloying technique at the temperature of 570 degrees C. The nitrided layers with different thicknesses and components were obtained by changing nitriding pressure. The microstructure and composition of the nitrided layers were evaluated by optical microscopy (OM) and X-ray diffraction (XRD). The wear properties of the nitrided layer against Al2O3 ball at room temperature using a ball-on-disc tribometer and against Si3N4 ball at elevated temperature using a HT-2001 abrasive wear test machine were investigated. The results show that the nitrided layers are composed of compound layer and diffusion layer at the pressure of 100 and 450 Pa. No obvious compound layer appears at pressure of 200 and 300 Pa. XRD analysis shows the nitrided layers are mainly composed of epsilon-Fe2-3N, gamma'-Fe4N, alpha-Fe, Fe2O3 and Fe3O4 phases. The surface hardness of plasma nitrided H13 steel is about 1100H-V-0.050 doubled that of substrate. The room temperature friction coefficient of H13 steel is reduced and wear rate is decreased by nitriding at 200 and 300 Pa. Elevated temperature wear test indicates the nitrided H13 steel at the pressure of 100 Pa shows lower friction coefficient and wear rate which are reduced more than 6 times compared with that of H13 substrate.

plasma nitriding; H13 steel; elevated temperature; wear

Taiyuan University of Technology; Ningbo University of Technology