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.