Effect of discharge current on the corrosion resistance and microstructure of ZrTiSiN coatings deposited by magnetron co-sputtering

ZrN coatings, modified by Ti + Si additions, were obtained by reactively co-sputtering elemental Zr and a TiSi alloy (29 %-at Si). The TiSi alloy target was sputtered at a fixed current, while the Zr target current was varied. By increasing the current applied to the Zr target (I_Zr = 550 mA, I_Zr = 750 mA, and I_Zr = 860 mA), the coating structure varied from predominantly amorphous to amorphous plus crystalline, and to predominantly crystalline. ZrTiSiN coatings displayed improved corrosion resistance compared to that of the binary ZrN coatings, which were studied as a reference. The coatings obtained at I_Zr = 550 mA displayed impaired protection against corrosion, which was attributed to a higher concentration of defects (droplets). The coatings obtained at I_Zr = 750 mA were studied with atom probe tomography to evaluate the interaction of the electrolyte with the columnar boundaries and understand the corrosion mechanism. The I_Zr = 750 mA coatings are of particular technological interest due to their outstanding corrosion resistance and high hardness.