Influence of the Cr interlayer on the microstructure of sputtered TiN coatings deposited on zirconium alloy

On the surface of zirconium alloy, the TiN coatings with and without Cr interlayer were prepared in the N-2/Ar mixed gas atmosphere by physical vapor deposition technology. The coatings morphology, micro-composition of surface particles, surface roughness, phase constituent and high-temperature oxidation resistance were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), roughness measuring instrument, x-ray diffractometer (XRD) and chamber electric furnace, respectively. The results show that, in comparison with the TiN coatings, the gray large particles increase in volume and the striated gullies reduce significantly for the Cr/TiN coatings. With the presence of Cr interlayer, the roughness of coatings increases, TiN (111) plane shows a weak growth, and the average grain size becomes small, while the average compressive strain increases. After the high-temperature oxidation test, there is a dense mixture of TiO2 and Cr2O3 on the surface of the Cr/TiN coatings which is continuous and complete without any defects such as cracks and holes. The Cr/TiN coatings enhanced the oxidation resistance of zirconium substrate, evidenced with 1/3 oxidation weight gain of that of the zirconium alloy. These results demonstrate the effectiveness of Cr/ TiN coating as a protective coating on the zirconium alloy under extreme conditions.