鈦合金(Ti-6Al-4V)為先進之航太材料，於常溫下具有高強度(950 MPa)且具有優異之抗潛變(900 MPa)與高溫強度(800 MPa @ 400 °C)，但於實務應用上為一難切削材料。Ti-6Al-4V合金擁有低彈性模數(~120 GPa)，於切削過程中造成刀具之反覆負載與疲勞破壞。低熱傳導係數(~7.5 W/m･k)造成切削熱聚集於剪切區附近，導致切刃軟化。本研究以乾式切削、溢流切削與極低溫切削環境輔助繞切鈦合金材料，實驗使用碳化鎢與類鑽碳鍍層之球刃刀具材料，耦合0.2-0.45 mm/rev之進給率，於固定40 m/min之切削速度及1 mm之切削深度，進行繞切實驗。透過基礎力學理論計算材料強度，並由實驗驗證操作參數與切削力、切削溫度、刀具磨耗與材料次表面硬度之物理效應。研究結果顯示，碳化鎢刀具於乾式切削耦合0.2 mm/rev進給率產生之切削力比類鑽碳鍍層刀具可降低14.6%，起因於材料產生熱軟化效應。當提高搭配進給率至0.45 mm/rev時，類鑽碳鍍層刀具產生熱擴散磨耗與侵蝕磨耗，破壞刀具幾何因而提高切削力，促使加工表面產生應變硬化而提高材料強度，直至切刃之破壞。類鑽碳鍍層刀具於溢流切削環境耦合0.2 mm/rev進給率時，鍍層之潤滑與散熱優勢可以維持，相比碳化鎢刀具可降低33.0%之切削力與22.9%之刃口磨耗。當使用液態氮降溫於切削切刃時，液態氮之冷卻效果可抑制切刃熱軟化與刃口之磨耗，進而降低切削力，維持低材料強度。但切削距離達一臨界值時，液態氮之降溫效應無法抑制刀具磨耗，造成切刃之破壞。

Ti-6Al-4V is an advanced aerospace material with high strength (950 MPa) at room temperature, excellent creep resistance (900 MPa) and high-temperature strength (800 MPa @ 400 °C), but it's a difficult-to-cut material in practical application. The low modulus of elasticity (~120 GPa) of Ti-6Al-4V causes the tool to be repeatedly loaded during the cutting process, resulting in fatigue damage. Low thermal conductivity (~7.5 W/m･k) causes cutting heat to accumulate in the shear zone, resulting in softening of the cutting edge. In this research, dry, flooding and cryogenic cutting environments are used to assist routing of Ti-6Al-4V material. The experiment uses ball end mill with tungsten carbide and diamond-like carbon coatings, couples the feed rate of 0.2, 0.3 and 0.45 mm/rev. The cutting speed of 40 m/min and the cutting depth of 1 mm are fixed to process the material. And the evolution of cutting force, cutting temperature and tool wear is recorded during the process. The material strength is calculated through basic mechanics theory, and the physical effects of operating parameters and cutting force, cutting temperature, tool wear and material subsurface hardness are verified by experiments. The research results show that the cutting force generated by coupling 0.2 mm/rev of tungsten carbide tools in a dry environment can be reduced by 14.6% compared with that of DLC-coated tools. When the feed rate is increased to 0.3 mm/rev, the thermal softening effect of the material will reduce the strength of the material. When combined with a high feed rate of 0.45 mm/rev, the diffusion wear and erosion wear of the DLC-coated tool due to cutting heat will promote strain hardening on the machined surface, increase the strength of the material and cause damage to the cutting edge. When the diamond-like carbon coating tool is coupled to 0.2 mm/rev in the flooding cutting environment, it can maintain the lubrication and heat dissipation advantages of the diamond-like carbon coating. Compared with the tungsten carbide tool, it can reduce the cutting force by 33.0% and the flank wear by 22.9%. When liquid nitrogen is used to cool the cutting edge, the flushing effect of liquid nitrogen can inhibit the thermal softening of the cutting edge and wear of the cutting edge, thereby reducing the cutting force and maintaining low material strength. However, when the cutting distance reaches a critical value, the cooling effect of liquid nitrogen cannot suppress the wear of the tool, resulting in damage to the cutting edge.

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