Corrosion and Wear-Corrosion Studies of Nitrides Coatings Obtained by Reactive Sputtering

摘要

Ceramic coatings such as TiN, or other nitrides and carbides produced by physical vapour deposition(PVD) are frequently used to increase the service life of tools.In the literature it is possible to find many articles about the wear or corrosion resistance of thesematerials but very few works which regard wear and corrosion phenomena occurring at the sametime.In this work we have studied TiN and (Ti,Cr)N with 1 urn thickness coatings deposited by reactivesputtering on stainless steel. In order to minimise coating porosity and defects some samples wereprepared as a multilayer coating with a 2000A thick Ti first layer and a 8000A nitride top layer.At first the corrosion resistance properties were evaluated in acid and in sodium chloride aeratedsolutions using potentiodynamic plots. The chromium presence in coatings increases corrosionresistance.Later the samples' corrosion behaviour was characterised during wear. An appropriate machine wasused which permitted electrochemical measurements during wear testing. By monitoring E_(COTT) andelectrochemical impedance spectroscopy during testing time, the effect of various loads andcounterface types on corrosion behaviour can be observed. The influence of the presence ofchromium in coatings and of a titanium underlayer can also be observed. (Ti,Cr)N deposits, whichhave the best corrosion resistance, prove to be the least resistant coatings to the wear-corrosionprocess as confirmed by microscopical observation.