雙軸超音波及雷射輔助切削技術應用於鎳基超合金銑削之研究

Application of Biaxial Ultrasonic and Laser Assisted Machining Techniques for Inconel 718 Milling

楊秉學(Bing-Hsueh Yang)

指導教授 ： 林盛勇

國立虎尾科技大學/工程學院/機械與電腦輔助工程系碩士班/碩士(2017年)

摘要

鎳基超合金是一種時效硬化的Fe-Cr-Ni基變形高溫耐熱超合金，它具有較高的高溫強度、良好的抗氧化性、抗熱腐蝕性、斷裂韌性和疲勞性能，近年來被廣泛地運用於火箭發動機及航空飛機的耐熱零件。而鎳基超合金也具有高強度、低熱傳導率、易產生加工硬化等性質，導致在加工過程中刀具易產生快速磨損，嚴重加工表面傷害等缺陷，因此，改善鎳基超合金切削性能、加工表面品質及刀具壽命的提升為長期以來相關業者最關心的課題。
本文建構共五階段鎳基超合金銑削實驗，包含無輔助、各單項輔助及多項混合輔助系統以驗證輔助效果之差異及優劣。首先，第一階段進行無輔助銑削以監測切削性能之變化及加工參數之調整。接著，在第二階段導入雷射系統，設定雷射與刀具間距離，測試雷射預熱是否能有效地降低切削力，第三至第四系統將超音波輔助銑削系統架設於工具機工作台上，測試、調校與修飾以確保單、雙軸振盪作動確實，最後第五階段將雙軸超音波輔助結合雷射輔助系統以建構一混合式輔助切削加工系統。實驗中同時觀測表面粗糙度、表面形貌、邊緣形貌及刀具磨耗於各加工參數之變化趨勢，期提高此難切削材的可切削性，進而取得更好的表面粗糙度、表面形貌與刀具磨耗。本文實驗採用耐磨耗、低摩擦係數的nano-Si®鍍層圓鼻鎢鋼端銑刀，透過加工製程參數（主軸轉速、徑向銑削深度、進給速度）全因子組合的調變規劃，針對鎳基超合金進行上述五階段之銑削加工。於實驗過程中，使用動力計監測銑削力的變化，以工具顯微鏡觀測加工完成表面形貌與邊緣形貌，並以接觸式表面粗度儀進行表面粗糙度之量測。結果顯示，雷射預熱輔助可有效地減低切削力並提升切削性能，雙軸超音波雙軸振盪則可以大幅度提升刀具壽命，結合以上二種輔助系統的雙軸超音波雙軸振盪混合雷射預熱輔助銑削系統，各項表現上皆優於無輔助或各單項輔助系統，在使用參數為主軸轉速6000rpm、徑向切深0.01mm、進給率300mm/min時，求得本實驗的最佳表面粗糙度0.216μm，刀具磨耗13.849μm。明顯地改善刀具磨耗與表面粗糙度。

關鍵字

Inconel 718 ； 超音波輔助 ； 雷射預熱輔助 ； 切削性能

並列摘要

The high temperature heat-resistant alloy such as Inconel 718 is a kind of Fe-Cr-Ni based super alloy through age-hardening treatment. It possesses high yield and ultimate strength, high fatigue strength, high working temperature, good corrosive resistance. It has been widely used for aerospace and other components that operate at high temperatures and hostile environments; such as, gas turbine, rocket engines, missile parts and hot extrusion tooling. However, these unique and desirable heat-resistant characteristics of super-alloys, on the other hand, impair their machinabilities greatly resulting in low material removal rate, short tool life and poor surface finish. Therefore, the cutting performance promotion and machined surface quality improvement of Inconel 718 resulting in extending the cutting-tool service life has long been the most concerned issue for related manufacturers.
The five stage experiments including without assistance, single and hybrid assisted machining systems on Inconel 718 milling were constructed in this study in order to verify the assisted effect on cutting performance and to compare the difference, merit and drawback among them. First of all, the milling experiment without assistance was performed to investigate the variations of cutting performance and the results were used for the suitable process parameter planning in the subsequent stage experiments. Next, a laser assisted system was introduced in the second stage where the spacing distance between the laser spot and cutting-tool along the cutting direction was set to test whether laser preheating may effectively reduce the cutting force. A biaxial ultrasonically assisted system with only one-axis oscillation (x or y direction) and with simultaneous two-axis oscillations (x and y direction) were subsequently introduced at the third to fourth stage experiments, respectively. While a biaxial ultrasonically and the laser assisted systems are integrated together to construct a hybrid assisted cutting system at the last stage experiment. Under these assistances, milling experiments of Inconel 718 by cutting-tool of tungsten carbide with nano-Si® coating were conducted. And the full factorial experiments of process parameter combinations such as spindle speed, radial cutting depth and feed rate were also planned. During the experiments, dynamometer is used to monitor the variation of cutting force. Tool wear, machined surface and side-edge surface morphology of the workpiece were measured by tool-microscope off-line. Surface roughness measurement through a probe contact type instrument was also performed. The results indicated that the laser-preheating assisted system could effectively reduce the cutting force as well as enhance the cutting performance. The effect of the biaxial ultrasonic oscillation on tool service life could greatly be promoted. Furthermore, the cutting performance exhibited in the integrated hybrid assisted milling prevails over that in milling without assistance as well as with each single assisted system. Under this hybrid assisted, the better surface roughness of 0.216μm was obtained at spindle speed of 6000 rpm, radial cutting depth of 0.01 mm, and feed rate of 300mm/min, accompanied by a maximum cutting-tool wear of 13.849μm. Because the use of this integrated hybrid assisted system, the cutting performance of tool wear and surface roughness could be improved significantly.

並列關鍵字

Inconel 718 ； biaxial ultrasonically assisted ； laser-assisted ； cutting performance

參考文獻

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