High-temperature tribological behaviours of H13 hot work mould steel by low-temperature plasma nitriding process

H13 hot work mould steel was treated via low-temperature plasma nitriding (LTPN) to obtain a nitrided layer. The morphologies, phases and hardness of the nitrided layer were characterised using a scanning electron microscope (SEM), X-ray diffraction (XRD) and Vickers hardness tester, respectively. The friction-wear behaviours of the nitrided layer at 500°C were investigated using a wear tester, and the effects of normal loads on the coefficient of friction (COF) and wear rate were discussed. The results show that the nitrided layer was composed of γ’-Fe4N and ϵ-Fe2–3N hard phases. The average COFs of the nitrided layer under the normal loads of 2, 4 and 6 N were 0.85, 0.57 and 0.50, respectively; and the corresponding wear rates were 7.30 × 10−5, 6.96 × 10−5 and 1.40 × 10−4 mm3 N−1 m−1, respectively, indicating that the wear resistance under the normal load of 4 N is the best among the three kinds of normal loads. The nitrided layer effectively improves the anti-wear performance of substrate, and the oxidisation wear decreases with the increase of normal load.