Effects of MQL on tool wear mechanisms in side milling of Ti2AlNb intermetallic alloys

Ti₂AlNb intermetallic alloy is a promising material for key aero-engine components, but its high-temperature strength, strong resistance to plastic deformation, and low thermal conductivity make it a typical difficult-to-cut material. In this study, minimum quantity lubrication (MQL) was applied to improve its machinability, and the effects of MQL on tool wear mechanisms during side milling were investigated. Compared with dry cutting, MQL significantly reduced milling forces, mitigated material adhesion, suppressed built-up edge (BUE) formation, and delayed tool wear progression. Under dry cutting, tool failure occurred when flank wear width reached 0.23 mm, whereas under MQL, failure was primarily characterized by chipping. Tool life under MQL reached 739.2 s, which was 3.28 times longer than under dry cutting (172.8 s). Milling forces under dry cutting rose rapidly from 34.68 N to 67.71 N within 172.8 s (an increase of 33.01 N). By contrast, under MQL, forces increased more moderately from 33.55 N to 38.90 N over the same period (an increase of only 5.45 N). At tool failure, the maximum milling force under dry cutting (67.71 N) was 1.74 times that under MQL (38.90 N). The dominant wear mechanisms under both conditions were adhesive wear and oxidative wear. These findings demonstrate that MQL enhances the machinability of Ti₂AlNb, reduces machining costs, and supports its broader application in aero-engine components.