The effect of Ti(CN)/TiNb(CN) coating on erosion-corrosion resistance

The goal of this work was to study electrochemical behaviour in corrosion-erosion conditions for Ti(CN)/TiNb(CN) multilayer coatings having 1, 50, 100, 150 and 200 bilayer periods on AISI 4140 steel substrates by using a multi-target magnetron reactive sputtering device, with an r.f. source (13.56 MHz), two cylindrical magnetron cathodes and two stoichiometric TiC and Nb targets. The multilayers were evaluated by comparing them to corrosion, erosion and erosion corrosion for a 30º impact angle in a solution of 0.5 M NaCl and silica, analysing the effect of impact angle and the number of bilayers on these coatings' corrosion resistance. The electrochemical characterisation was performed using electrochemical impedance spectroscopy for analysing corrosion surface; surface morphology was characterised by using a high-resolution scanning electron microscope (SEM). The results showed a decreased corrosion rate for multilayer systems tested at 30°.