Abstract
The objective of this study was to deposit thick TiZrN coatings with Ti interlayer above 3 μm on AISI D2 steel by dc unbalanced magnetron sputtering and investigated the effect of Ti interlayer on mechanical properties, simultaneously. The controlling deposition parameters were the adding of Ti interlayer and thickness of the coating. The Ti0.75Zr0.25N coating was selected due to the lowest residual stress comparing with Ti0.45Zr0.55N and Ti0.15Zr0.85N. There were three experimental conditions, namely, TiN(t) coating, TiZrN(tz) coating, and TiZrN/Ti(tzt) coating. The results showed that TiZrN coating with Ti interlayer, which thickness up to 3 μm were successfully deposited on D2 steel substrate. The N/Ti ratio for TiN coatings and N/(Ti+Zr) ratio for TiZrN coatings were nearly constant ranging from 1.0 to 1.2 and Zr/(Zr+Ti) ratio for TiZrN coatings were about 0.25. The hardness of TiN coatings was 24.2 and 26.2 GPa and the hardness of TiZrN coatings higher than 30 GPa. The texture of TiZrN coatings were with strong (111) by adding the Ti interlayer when the thickness of TiZrN coating smaller than 1 μm. The residual stress of TiZrN coatings was higher than TiN coatings and the residual stress were released by adding Ti interlayer. The residual stress of tzt-series was about constant until the TiZrN coating thickness reached 1 μm, then the residual stress increased with increasing TiZrN coating thickness. This pointed out the limitation of stress relief by adding Ti interlayer. From the results of scratch test, the adhesion of TiZrN/Ti coating slight increased. In the wear test, the coating with higher toughness possessed better wear resistance; meanwhile, the coating with smaller store energy possessed better wear resistance. The effect of store energy and toughness were the dominate factors on the wear resistance of coatings.