The Fabrication And Properties Of Chromium Nitride Films On Commerical Iron

In order to improve anti-corrosion properties of the iron, Cr-N films, Cr/CrN multilayer films and Ti/TiN/Cr/CrN multilayer film with different composition, structure were deposited on commercial pure iron by unbalanced magnetron sputtering system. The thickness and residual stress of the films were tested using profile meter. The structure and composition were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The microhardness, wear resistance and adhesion strength between films and substrate were analyzed with microhardness meter, CSEM pin-on-disk wear test apparatus and scratch tester. The corrosion resistance was studied by using electrochemical method and exposuring in 300°C thermal humid vapour ambient. The porosity ratio was calculated using coulometric method based on the polarization curves obtained in the 30g/L NaCl solution at room temperature. Main results were concluded as follows:1. The Cr-N films with different structure and properties were synthesized at different N₂ flow. The results showed that the film consist of Cr and Cr₂N phase, which deposited at 6scccm N₂ flow, had compressive residual stress and high microhardness; The film deposited at 20scccm N₂ flow, which consist of Cr₂N and CrN, showed low tensile stress, good wear and corrosion resistance; The film deposited at 30scccm N₂ flow , which consist of CrN phase, exhibited low residual stress, excellent adhesion strenth between film and substrate, good wear and corrosion resistance. The bias voltage of the films were setted from -50V to -150V. It is found that the microhardness and the compressive stress of the films increased with the bias voltage increasing. The wear and corrosion resistance decreased with the bias voltage increasing.2. The Cr/CrN multilayer films with different periods were synthesized on iron to restrain the growth of the columnar microstructure. The Cr/CrN multilayer film produced with period 180s showed an excellent periodicity, which had excellent adhesion strength between the film and substrate. The potentiodynamic polarization obtained in 30g/L NaCl solution showed the Cr/CrN multilayer film could significantly improve the corrosion resistance of iron. The thermal vapour ambient exposure experiment showed the Cr/CrN multilayer film produced with period 180s provided the best protection for iron. The Cr/CrN multilayer film showed better anti-corrosion property than CrN single film.3. Comparing with iron modified by Cr/CrN multilayer film deposition, the iron with plasma nitriding and Cr/CrN multilayer film duplex modification exhibited better wear and corrosion resistance. The Cr/CrN multilayer film showed much better corrosion resistance and lower porosity ratio than Ti/TiN/Cr/CrN multilayer film. However, Ti/TiN/Cr/CrN multilayer film had better wear resistance.