Study on the preparation process of Ti coatings on ZrO₂ balls by mechanical milling coating technology

The titanium (Ti) coatings were prepared on the surface of ZrO₂ balls in the average diameter of 1 mm by mechanical milling coating technology. The influences of milling time, ball-to-powder weight ratio, and milling atmosphere on the formation of titanium coatings were systemically investigated. The microstructure and physical properties of titanium coatings were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and ultrasonic wave. The results show that, the thickness of titanium coatings firstly increases and then decreases with the increasing of milling time and ball-to-powder weight ratio. The average thickness of the coating milled for 30 h reaches the maximum as about 76 μm. Meanwhile, the ball-to-powder weight ratio of 2.5:1.0 can provide the maximum average thickness of Ti coatings (about 73 μm). The binding strength of titanium coating increases first andthen decreases with the increasing of milling time. The forming time of coatings can be shortened by increasing the ball-to-powder weight ratio properly. The titanium powders in the ball-mill can be easilty oxidized to TiO by the intermittent air introduction, which further hinders the formation of coatings. So, the sealing state in ball milling process is more beneficial to the formation of titanium coating.