Martensitic Stainless Steels Low-temperature Nitriding: Dependence of Substrate Composition

TL;DRAbstract

Low-temperature plasma assisted nitriding is a very promising technique to improve surface mechanical properties of stainless steels, keeping unaltered or even improving their surface corrosion resistance. During treatment, nitrogen diffuses into the steel surface, increasing its hardness and wear resistance. In the present work the nitriding process of different martensitic stainless steels was studied. As-quenched AISI 410, 410NiMo, 416 and 420 stainless steel samples were plasma nitrided at 300, 350, 400, 450, and 500°C, for 4 h, at 3 Torr, in a gas mixture of 70% N2 + 20% H2 + 10% Ar, and flow rate of 3.33×10–6 Nm3s−1. The study of the nitrogen-rich layer thickness indicates two different activation energies, one for low (<400°C) and another one for high temperature ( ≥400°C), except for the AISI 410NiMo. The surface hardness increases with temperature for all steels between 300 and 450°C. For 500°C, except for the AISI 410NiMo, the surface hardness decreases if compared to that ob

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