Corrosion, Erosion and Erosion-Corrosion Performance of Plasma Electrolytic Nitrocarburising (PEN/C) on AISI 4140 Steel

Plasma electrolytic nitro carburizing (PEN/C) has been used to the surface to modify AISI 4140 steel to a depth of approximately 200 JlID of compound and diffusive layer. Potentiodynamic polarizations and electrochemical impedance spectroscopy (EIS) have been made under static conditions in order to evaluate the corrosion erformance ofPEN/C coatings. The erosion and erosion--corrosion perfoIlll8DCe of the PEN/C coating has also been assessed with a rotating disk electrode at specified rates of stirring. with and without a given potential to the sample. The erosion and erosion--corrosion tests were carried out using sub angular sand particles ranging in size from 135 to 235 )lm. Scanning electron microscopy (SEM) was used to investigate the coating microstructure and the coating/substrate interface. The analysis shows that the PEN/C nitro carburized coatings studied in this investigation had a pore/crack network to the steel substrate, which compromised the corrosion and erosion-corrosion perIDllDance.

Keywords:

Erosion , Plasma Electrolytic Nitro Carburizing , Surface modification , Rotating disk electode