Fundamental Research on the Ultrasonic Assisted Plasma Oxidation Modification Grinding of Titanium Alloy

In view of the poor grindability of titanium alloys, a new machining process, i.e., ultrasonic assisted plasma oxidation modification grinding (UAPOMG), is proposed to improve the grindability of the titanium alloys. The machining principle of the UAPOMG is introduced first, and the experimental apparatus is constructed based on the machining principle. Secondly, the effects of different electrolytes on the growth direction of the plasma oxidized layer and process parameters on the thickness of plasma oxidized layer are studied. Then, the main chemical composition and microhardness of the plasma oxidized layer are characterized, and the material removal behavior of the plasma oxidized layer is revealed by single point grinding experiment. Finally, the grinding performances involving titanium alloy samples with and without plasma oxidized layer are compared experimentally. The results show that the plasma oxidized layer mainly grows inward under the Na2SO4 electrolyte, and the slower feed rate and higher ultrasonic vibration amplitude give rise to the much thicker plasma oxide layer. Through the single point grinding test, it is found that the lower microhardness of the plasma oxidized layer with many cracks improves the grindability of titanium alloy. Compared with titanium alloy without oxidized layer, the oxidized layer obtained by the plasma with assistance of the ultrasonic vibration can reduce the grinding force and chip adhesion on the grinding wheel surface and improve the quality of the ground work-surface.