Laser Induced Oxidation Assisted Micro Milling Of TC4 Titanium Alloy

Titanium alloy has been widely used in all kinds of human implants,such as artificial bone,skeletal fixation device,cardiovascular stent,micro pump impeller and so on due to its high strength,good corrosion resistance,high heat resistance and good biocompatibility.However,there are still many problems in micro milling of titanium alloy due to its difficult machining characteristics,such as low tool life,poor machined surface quality and poor process controllability.In order to solve those problems,a new hybrid processing method named laser induced oxidation assisted micro milling of titanium alloy was proposed in this paper,and the related tests were carried out.The main contents and conclusions are as follows:(1)Based on the thermodynamic analysis of oxidation reaction,laser induced oxidation experiment of TC4 titanium alloy was carried out.The effects of average power,scanning speed and reaction atmosphere on the microstructure,thickness and composition of oxide layer and subsurface layer were studied.The results show that under suitable laser parameters and reaction atmosphere,the surface of TC4 titanium alloy can generate a porous oxide layer with thickness of 8~18.2?m and a dense subsurface with thickness of 0.5~2.6?m.The average power,scanning speed and reaction atmosphere have significant influence on the properties and thickness of the oxide layer and subsurface layer.(2)Based on the test results of laser induced oxidation,a hybrid processing method named laser induced oxidation assisted milling of TC4 titanium alloy was proposed.And the comparison test of laser induced oxidation assisted micro milling and conventional micro milling was carried out.The milling force,machined surface quality and tool wear in two processing methods under different feed rates and milling depths were studied.The results showed that on the premise of not affecting or even improving the quality of machined surface quality,the hybrid processing method of laser induced oxidation assisted milling of TC4 titanium alloy can effectively reduce the milling force in the milling process,reduce tool wear and prolong the service life of the tool.The feasibility of the new method is verified by the test.(3)Based on the test results of laser induced oxidation assisted micro milling,the laser assisted oxidation assisted micro milling and conventional micro milling tests with high aspect ratio micro groove structure(aspect ratio larger than 5)were carried out.By comparing the milling force,tool life and the quality of high aspect ratio microgrooves in two processing methods,it was found that hybrid processing method has more advantages in high aspect ratio micro groove processing compared with the conventional micro milling,which can greatly reduce the milling force in the process and improve the tool life and machining quality.The tool life can be increased by more than 2 times.