Effects of plasma nitriding in the corrosion behavior of an AISI 4140 steel using a seawater medium solution

In this work, a comprehensive analysis was performed to characterize the corrosion response of untreated and nitrided AISI 4140 steel. Samples were plasma nitrided at low temperature (similar to 400 degrees C) with two different gas composition. Electrochemical impedance spectroscopy, potentiodynamic polarization in artificial seawater solution at room temperature test were performed. Nitrided samples increases hardness on surface compared to the untreated sample. Nitrided samples composed by a mixture of epsilon-Fe2-3N and gamma'-Fe4N nitrides phases offered significant influence on anodic and cathodic polarization. Nyquist curves indicated a higher corrosion resistance of nitrided samples compared to untreated sample.

Automated summary

This work comprehensively analyzed the corrosion response of untreated and nitrided AISI 4140 steel. The nitrided samples showed increased hardness on the surface and the composition of nitride phases had significant influence on anodic and cathodic polarization. The nitrided samples exhibited higher corrosion resistance compared to the untreated sample.