High-temperature tribological behaviours of H13 hot work mould steel by low-temperature plasma nitriding process Comportements tribologiques a haute temperature de l'acier a moules pour travail a chaud H13 par procede de nitruration plasma a basse temperature

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 degrees 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 gamma'-Fe4N and epsilon-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 x 10(-5), 6.96 x 10(-5) and 1.40 x 10(-4) mm(3) 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.