Improving the Abrasive Wear Resistance of a Microalloyed Steel by Plasma Nitriding

The aim of this work was to study the micro-abrasive wear resistance of an API 5L X-70 microalloyed steel plasma nitrided under different conditions of time and temperature. Pulsed DC plasma nitriding experiments were performed under a treatment atmosphere of 10%N2 + 90%H2, at temperatures of 410, 440 and 470 °C and for nitriding times of 1, 3 and 5h. The results show that plasma nitriding performed at 440 °C and 1h led to the formation of a compound layer constituted mainly of ε-Fe2-3N nitride and a diffusion zone with large needle-like nitride, offering the highest wear resistance. The amount of γ’- Fe4N phase was found to increase with the plasma nitriding time, decreasing the wear resistance of the material.