Machinability improvement of titanium alloy in face grinding by ultrasonic assisted jet plasma oxidation

A novel machining technology, namely ultrasonic assisted jet plasma oxidation modification face grinding (UAJPMG), was proposed to improve the machinability of the titanium alloy, in which the titanium alloy materials are modified by plasma oxidation followed by face grinding. This paper introduced the processing principle of UAJPMG and the design of an ultrasonic jet nozzle to promote plasma oxidation. Using the ultrasonic jet nozzle produced in-house, the effect of the ultrasonic vibration on the plasma intensity was experimentally investigated. The results revealed that the application of ultrasonic vibration can diminish the thickness of the gas film by elevating the jet flow rate, thereby reducing the generation delay time and enhancing the plasma intensity. Subsequently, a scratch test was performed to assess the difference in the mechanical strength between the plasma oxide layer and the titanium alloy substrate. It was found that the plasma oxide layer with a reduced mechanical strength exhibited a deeper scratch depth under the same normal load. Based on these, the machining performance under different conditions was examined considering the removed material of the abrasive grains. Compared with the removed material was Ti-6Al-4V substrate in conventional face grinding, the ultrasonic assisted plasma oxidized material can inhibit the chip adhesion on the wheel working surface, resulting in a reduction of the grinding force and the surface roughness and an improvement of the groove shape accuracy. The novel machining technology, i.e., UAJPMG, proposed in this paper might provide a new approach for the precision machining of critical components made from titanium alloy.