Microstructure and mechanical, electrical, and electrochemical properties of sputter-deposited multicomponent (TiNbZrTa)Nx coatings

A series of (TiNbZrTa)Nx coatings with a thickness of similar to 1.1 mu m were deposited using reactive magnetron sputtering with segmented targets. The deposition temperature was varied from room temperature to 700 degrees C resulting in coatings with different microstructures. The coatings were characterized by electron microscopy, atomic force microscopy, compositional analysis, and X-ray diffraction. Effects of the deposition temperature on the electrical, mechanical and corrosion properties were studied with four-point probe, nanoindentation and potentiodynamic polarization measurements, respectively. X-ray photoelectron spectroscopy (XPS) analyses reveal a gradual change in the chemical state of all elements with increasing growth temperature from nitridic at room temperature to metallic at 700 degrees C. A NaCl-type structure with (001) preferred orientation was observed in the coating deposited at 400 degrees C, while an hcp structure was found for the coatings deposited above 400 degrees C. The resistivities of the TiNbZrTa nitride coatings were found to be around 200 mu Ocm. In 0.1 M H2SO4 aqueous solution, a corrosion current density of 2.8 x 10(-8) A/cm(2) and a passive behaviour up to 1.5 V vs. Ag/AgCl were found for the most corrosion resistant coating. The latter corrosion current is about two orders of magnitude lower than that found for a reference hyper-duplex stainless steel.