Improved machinability of TiB2-TiC ceramic composites via laser-induced oxidation assisted micro-milling

Low manufacturing efficiency, poor processing controllability and deteriorated surface quality were main challenges in micro-milling high hardness TiB2-based ceramic composites. This research work investigated an innovative hybrid machining method named laser-induced oxidation assisted micro-milling (LOMM) of TiB2-TiC ceramic composites with hardness of 20 +/- 0.7 GPa. Oxidation mechanism of the material under laser irradiation was studied. At single pulse energy of 0.275 mJ and scanning speed of 1 mm/s, the irradiated surface in an oxygen-rich atmosphere produced metamorphic layer including loose and porous oxide-layer as well as dense sub-layer with hardness of 9.6 +/- 0.7 GPa. In addition, the main compositions of formed oxides were anatase TiO2 and rutile TiO2, which can be easily removed with an extremely low cutting force. For the investigated range of milling parameters, the milling force and the machined surface quality were studied in LOMM of TiB2-TiC ceramic composites. A significant reduction (more than 70%) of milling force during removing the oxide-layer was obtained, compared to that milling of the sub-layer. Besides, a well-machined surface quality was obtained (a(p) = 2 mu m and f(z) = 0.5 mu m/z) with a ductile removal mode, and surface roughness is 146 nm. As a case study, a microgroove having a width of 0.4 mm and an aspect ratio of 2.5 was fabricated successfully using LOMM. As a comparison, under identical cutting parameters conventional micro-milling (CONM) was performed. The results indicated that machined quality of the microgroove and perpendicularity of the sidewall obtained by LOMM were superior to those using CONM. Machining efficiency was also improved significantly by 106% using LOMM, compared to CONM. It confirmed that the LOMM process was an efficient and effective method to machine high hardness ceramic composites.

Automated summary

The study investigated a novel hybrid machining method named laser-induced oxidation assisted micro-milling (LOMM) for high hardness ceramic composites, which significantly reduced milling force and achieved well-machined surface quality.