激光诱导可控氧化辅助微细铣削TiAl金属间化合物的研究

Investigation on Laser-induced Controllable Oxidation Assisted Micro Milling of Titanium Aluminum Intermetallic Alloy

TiAl金属间化合物微细铣削过程的高比切削力和微铣刀的弱刚性是导致微结构加工效率低、表面完整性差和工艺可控性低等问题的主要原因,本研究提出了激光诱导可控氧化辅助微细铣削复合加工新方法。在激光平均功率为4.5W、扫描速度为1 mm/s以及富氧环境下,激光诱导TiAl金属间化合物生成了疏松多孔的氧化物,氧化物能够被微细铣刀快速去除,且去除过程中切削载荷低,刀具几乎没有磨损。主要研究了激光辐照下TiAl金属间化合物的氧化机理;背吃刀量和每齿进给量的变化对铣削力、加工表面质量和刀具磨损的影响规律,并与常规微细铣削工艺进行了对比研究。结果表明:采用低的激光平均功率与扫描速度时,氧化反应平稳进行,且生成疏松多孔的氧化物,氧化物主要是钛矿型TiO2与金红石型TiO2,过渡层表面平整,有微裂纹产生以及少量残留的氧化物。相比于常规微细铣削工艺,激光诱导可控氧化辅助微细铣削工艺下的铣削力和刀具磨损较低。此外,当背吃刀量和每齿进给量分别为4μm和3.5μm/z时,可获得较好的加工表面质量,表面粗糙度达到128 nm。复合加工工艺中微细铣刀的失效形式为涂层脱落和材料黏结。与常规微细铣削工艺相比,激光诱导可控氧化辅助微细铣削工艺的刀具寿命显著提高。

The poor rigidity of micro tools and the high cutting force are the main reasons for the low manufacturing efficiency, poor surface quality and low processing controllability in micro milling of Ti Al intermetallic alloy. In this work, an innovative hybrid machining process of laser-induced controllable oxidation assisted micro milling(LOMM) is proposed. At average laser power of 4.5 W, scanning speed of 1 mm/s and oxygen-rich atmosphere, loose and porous oxide layer is produced, which is easy to be removed with extremely low milling force and no tool wear. The oxidation mechanism of the material under laser irradiation is revealed. In addition, the effects of depth of cut and feed per tooth on milling force, surface quality and tool wear are studied. For a comparison, conventional micro milling(COMM) is carried out under identical milling parameters. Results reveal that the oxidation reaction proceeds smoothly at a low average laser power and scanning speed. Loose and porous oxide is produced, which mainly consist of anatase TiO2 and rutile TiO2. In addition, the sub-layer is flat with micro-crack as well as small amount of remained oxides. The milling force and tool wear in LOMM are lower than those in COMM. At feed per tooth of 3.5 μm/z and depth of cut of 4 μm, surface roughness achieved in LOMM is 128 nm. The main wear types of the micro end mill in LOMM are coating spalling and adhesion. Compared with COMM, the tool life in LOMM is prolonged significantly.