Assessment of tribological properties of plasma nitrided 410S ferritic-martensitic stainless steels

Low Temperature Plasma Nitriding (LTPN) is a surface treatment that promotes surface hardening without harming the corrosion resistance of martensitic stainless steels. LTPN and conventional plasma nitriding (CPN) treatments were carried out to compare the influence of the obtained nitrided layers on the abrasive wear resistance of AISI 410S ferritic-martensitic stainless steel. The samples were plasma nitrided for 20 h in a gas mixture of 75% N-2: 25% H-2, at 250 Pa. LTPN was carried out at 400 degrees C, obtaining a 50 mu m thick expanded martensite layer. CPN done at 530 degrees C, resulted in a 170 mu m nitrided layer, with an outermost compound layer 15 mu m in thick. Nanoindentation tests to assess the mechanical properties and the energy dissipation coefficient were carried out. Scratch and micro-abrasion tests were conducted to evaluate the friction coefficients, failure modes, critical loads and wear resistance. Tensile cracking was the prevalent mechanical failure mode of the nitrided layers. Micro-abrasion results showed that LTPN and CPN samples exhibited similar wear volume losses. A change in the wear volume loss rate with sliding distance was observed for the nitrided samples. A change from grooving to rolling abrasion explains the change in the wear rate.