Fundamental Research On Laser Induced Controllable Oxidation Assisted Micro-Milling Of Ceramic Composites

Ceramic materials are widely used in aerospace,microelectronics,energy engineering,cutting tools and biomedical fields due to their high hardness,high strength,low density,low expansion coefficient,good wear resistance and chemical resistance.However,ceramic is typical difficult-to-machine material,and there are problems such as severe tool wear,low processing efficiency,and poor processing quality in micro-milling process.In order to solve the problems,a novel method of using laser-induced controllable oxidation to assist micro milling of the TiB₂-based ceramic composites was proposed in this paper,and related experimental research is carried out.The main work contents and conclusions are as follows:?1?Based on thermodynamic analysis of the oxidation reaction of TiB₂-based ceramic composites,laser induced oxidation experiments were carried out.Under laser irradiation,an oxidation reaction between ceramic composites and oxygen took place,forming a loose and porous oxide layer.The effects of average laser power,scanning speed and assistant gas on the morphology,phase composition,thickness and hardness of the oxide and subsurface layers were investigated in detail.The results show that increasing the average laser power,reducing the scanning speed,and higher oxygen content make the oxidation more sufficient.For the investigated range of parameters,the optimal laser parameters are average laser power of 5W and scanning speed of 1mm/s,under which the thickness of oxide and subsurface layers is 51?m and 15?m in an oxygen-rich environment,respectively.?2?The experiments of laser-induced controllable oxidation assisted micro-milling ceramic composites were carried out.The effects of feed per tooth and milling depth on milling force,surface morphology,surface roughness and tool wear were studied,and the ductile removal mechanism of the ceramic composites was revealed.The results show that the milling force increases with the increase of the feed per tooth and the milling depth.When the cutting speed is 31.4m/min,the milling depth is 2?m,and the feed per tooth is 0.3?m/z,the ceramic material can be removed in ductile mode,with a surface roughness Ra of 46 nm and Sa of 60 nm;and the main form of tool wear is flank wear and coating shedding.?3?The laser-induced controllable oxidation assisted micro-milling process scheme for ceramic composite microstructures was developed.And a micro-groove with a width of 0.5 mm and an aspect ratio of 2 was successfully fabricated.The comparison experiment between hybrid process and conventional micro-milling was carried out.The results show that the milling force increases slowly with the increase of material removal amount in the hybrid process,while which increases sharply in the conventional micro-milling process,and the tool fracture occurred when the machining depth reached 0.114 mm.The micro-groove prepared by the hybrid process are superior to the micro-groove prepared by the conventional micro-milling process in terms of contour accuracy,edge defect size,and groove bottom surface quality.In addition,the hybrid processing successfully increases processing efficiency by 105%,compared with the conventional micro-milling process.