An effort towards hard and tough coatings by cathodic arc deposition of Zr-Cr-O coating system

A new coating system of Zr-Cr-O in which tetragonal ZrO2 acts as toughening agent and Cr2O3 can act as stabilizer and hard matrix was proposed. The coatings were obtained by cathodic arc deposition of Zr and Cr in gas mixture of oxygen and argon. Pure ZrO2 coatings were also deposited as control group to verify the stabilizing effect of Cr in tetragonal ZrO2. Various substrate biases were applied to modify the properties of the coatings. The result showed that monoclinic phase dominated in pure ZrO2 coating, whereas only tetragonal phase can be detected in ZrO2 coating with low Cr content. Increasing of Cr content resulted in more and more amorphous phase until crystal Cr2O3 was obtained when Cr content was higher than 90.27%. The phase composition was also affected by substrate bias. It was found that tetragonal phase in pure ZrO2 was destroyed when substrate bias was applied, whereas tetragonal phase in Cr-doped ZrO2 was very stable, and the crystallinity of the co-deposited coatings was enhanced by substrate bias. The hardness of the coatings was affected by composition, substrate bias and crystallinity. It was regretful that Cr doped t-ZrO2 coatings showed relatively low hardness due to high amount of amorphous phase. However, a remarkable plastic deformation capability was found in all the co-deposited coatings, and the coating with high Cr content and high bias voltage exhibited relatively high hardness, H/E and plastic deformation.