Tribocorrosion behaviour of duplex surface treated AISI 304 stainless steel

This paper reports on the corrosion and tribocorrosion behaviour of AISI 304 stainless steel surfaces after processed by a duplex treatment consisting of plasma nitriding and a CrN coating by physical vapour deposition (PVD). An industrial evaporation PVD reactor chamber has been adapted to produce a nitriding layer using arc-enhanced glow discharge (AEGD) in the presence of nitrogen gas. Subsequently, CrN coatings were deposited in the same chamber without disrupting the vacuum cycle. Nitrogen diffusion layers of up to 12 μm thick were produced on the AISI 304 steels in a 2 h process. Hardness of the nitrided steel surfaces increased by a factor of 5.5 with respect to the pristine steel surfaces. The hardness of the duplex layer reached 10.700 N/mm2, which resembles the values typical for a CrN coating on tool steels. The electrochemical results revealed that the duplex treated steels exhibit similar corrosion current density to the pristine surfaces but lower susceptibility to localised corrosion. Moreover, the duplex treated steel presents a total wear volume loss after a tribocorrosion test one order of magnitude lower than that exhibited by the pristine substrate. As an overall conclusion, CrN duplex treatments have enhanced both the mechanical properties and the electrochemical behaviour of the AISI 304 steel in the presence of friction conditions.