A nitrided case composed of expanded martensite and small quantities of hexagonal ε-Fe24N10 iron nitrides was formed in a martensitic stainless steel by means of active screen plasma nitriding process. Nanoindentation tests were carried out in order to assess the mechanical properties and to obtain an energy dissipation coefficient defined as the ratio of plastic to total deformation energy. Friction coefficient, mechanical failure mode and critical load for damaging the nitrided case were determined using linear scratch tests performed at both linearly-increased normal force and constant normal force according to ASTM C1624 standard. The scratch test results showed that the groove features and the friction coefficient could be well correlated to the energy dissipation coefficient. The expanded martensite strongly decreased the friction coefficient in comparison to the non-nitrided martensitic stainless steel. The critical load was 14 N and tensile cracking was the mechanical failure mode of the nitrided case.
- Mechanical failure mode
- Expanded martensite
- Scratch test
- Active screen plasma n0itriding