Plasma nitriding and post-oxidation metallic materials

by Prof. Carlos A. Figueroa (Universidade de Caxias do Sul - Brazil)

Thursday 6 Sept 2012, 15:00 → 16:00 Europe/Rome

Rostagni (INFN)

The surface modification of metal alloys through plasma technologies has gained new applications in the last years. In particular, plasma-assisted diffusion technologies like plasma nitriding is an established technique owing to the formation or/and precipitation of metallic nitrides which can improve the surface mechanical properties such as hardness, fatigue, and wear resistance. Moreover, plasma post-oxidizing can improve the corrosion resistance and decrease the friction coefficient of nitride layers. Among the most important results, oxygen creates a potential barrier blocking nitrogen incorporation. Moreover, oxygen adsorption follows a Langmuir Isothermal. Chemically, this barrier is formed by metallic oxides and the lower nitrogen retention on surface is due to the degradation of metallic nitrides. Although hydrogen and deuterium remove oxygen from surface in plasma nitriding processes, deuterium shows a greater removal rate than hydrogen. In addition, xenon induces defects, nano-texturing the surface and improving the nitrogen diffusion into bulk material. On the other hand, hydrogen allows controlling the types of oxides in post-oxidation processes of nitrided layers. Nitridation or post oxidation is a powerful method to create a protection against liquid metal embrittelment.