Elaboration de dépôts nano-composés par pulvérisation cathodique magnétron pour la substitution du chrome électrolytique
This research focuses on the synthesis and characterization of CrN based multilayer coatings for the replacement of electrolytic chrome. The studied materials include chromium nitrides coatings Cr-Zr-N ternary multiple phase and multilayer coatings and Si added CrN / ZrN multilayer coatings. The main objective of this thesis si to deposit the controllable coating structure and properties based on a magnetron sputtering technology so that the coating performance can be optimized to satisfy the replacement of Cr in industry scale. Coating structures are characterized by various techniques such as glow discharge optical spectrometer (GDOS), X-ray diffraction (XRD), scaning electronic microscope (SEM), transmission electronic microscope (TEM). The mechanical, tribological and corrosion properties of the deposited coatings are evaluated using nanoindentation, scratch test, pin-on-disk, dynamic polarization techniques respectively. The first study is related to chromium nitride coatings with controllable structure; The hysteresic curve and target voltage versus nitrogen flow rate curve are used to predict the phase evolution on chromium nitride. Optical emission spectroscopy (OES) analysis for various RF biases reveals that the increased substrate bias leads the nitrogen content to decrease. The second study is concentrated on Cr-Zr-N system. Solid solution CrN(Zr) coatings and nanoscale multilayer CrN/ZrN coatings with bilayer thickness (^) ranging from 11. 7 to 66. 7 nm are prepared. CrN(Zr) coatings show a maximum hardness value of approximately 24 GPa while CrN / ZrN multilayers present constant hardness of 29 GPa. In corrosion tests, these coatings show good chemical inert and very low corrosion current densities. To enhance the performance of CrN / ZrN multilayers, a further effort to add Si into CrN / ZrN multilayer is carried out. The deposited CrSiN / ZrN multilayer coatings with ^ from 13. 4 nm to 86. 9 nm have nanocrystalline/amorphous structure (nc-CrSiN / a-ZrN). They demonstrate elevated corrosion potentials in comparison with the single layers. On the other hand, CrN / ZrSiN multilayers with ^ from 11 nm to 153 nm form nancrystalline/amorphous period structure (nc-CrN / a-ZrSiN). This multilayer structure shows a good combination of high hardness from ZrSiN and good toughness from CrN. The addition of Si into ZrN individual layer has been shown to be an efficient way to inhibit pitting corrosion.