臺灣博碩士論文加值系統

直接式雷射沉積法為一種積層製造工法，其過程為金屬粉末通過高能量雷射光束後，熔融沉積於基板，形成熔覆層。然而，熔覆層之幾何外型會隨著製程參數的變動，而有不同的外型特徵；對於雷射沉積技術的使用者來說，製程的供粉質量流率、供粉氣體積流率、雷射功率、雷射掃掠速率均為影響熔覆成型之重要參數。若是無法掌控上述工作參數，除了無法確保熔覆層高與層寬品質，進而將無法規劃積層製程，並且造成熔覆材料、工件、載體氣體與時間等成本的浪費。
針對上述雷射沉積的技術挑戰，本論文以Stellite 6粉末為熔覆材料、中碳鋼S45C為基材，對熔覆層層高、層寬進行成型參數研究，以改善熔覆製程。同時，針對與熔覆層高相關的供粉質量流率、供粉氣體積流率、雷射功率、雷射掃掠速率參數，利用田口法進行兩階段優化實驗設計，求得熔覆層高介於1.4 mm至0.4 mm間，在此層高範圍下可提升積層效率。接著，關於熔覆寬度實驗，將實際成型熔覆寬度範圍2.0mm至3.0mm，對應至所建立之高斯雷射能量密度模型，找出成型寬度邊界之功率密度臨界值，可依據給定的雷射功率與雷射掃掠速率，作為熔覆寬度參考依據。為滿足雷射積層成型之應用需求，綜合熔覆層層高與層寬的實驗結果，進行多道熔覆路徑重疊率實驗。挑選0.25至0.35之六組高寬比，分別進行25%、30%、35%、40%、45%、50%多道重疊率實驗，並以最大波紋輪廓值作為判斷熔覆品質之依據。綜合本文研究成果，可提供直接式雷射沉積製程使用者，一套從單道熔覆至多道熔覆之積層參數資料庫。

Direct laser deposition is a category of additive manufacturing. Its process lets metal powder be fed through a coaxial high-energy laser beam, then the melted powders drops into the molten pool and deposits on the substrate to form a cladding layer. However, the geometry of the cladding layer varies with the process parameters. For the users of the laser deposition technique, the powder mass flow rate, carrier gas flow rate, laser power and scan rate, affecting the cladding, are important parameters. If these working parameters can’t be controlled, the quality of the cladding layer height and layer width would not be ensured. In addition, it might cause waste of cladding materials, workpieces, the carrier gas, and time, etc.
In response to the technical challenges of the laser deposition, Stellite 6 powder chosen as cladding material and the medium carbon steel S45C selected as the substrate were used to experiment the cladding layer height and layer width of the forming parameters for improving the cladding process. First, the two-stage optimization experiment was carried out by using Taguchi method with the mass flow rate, carrier gas flow rate, laser power, and scan rate as parameters. The result shows the cladding layer height between 1.4 mm and 0.4 mm the additive layer is effective and easy to achieve under this range of layer height. Then, the cladding layer width between 2.0 mm to 3.0 mm was tested to map to the established Gaussian laser energy density model, and to find the power density threshold of the forming width boundary. According to the given laser power and scan rate, based on the Gaussian laser energy density model, the cladding layer width can be predicted. In order to meet the application requirements of laser deposition, the multi-track cladding path overlap were tested by combining the results of cladding layer height and layer width experiments. By selecting the aspect ratio between 0.25 to 0.35, and setting the overlapping rate as 25%, 30%, 35%, 40%, 45%, and 50%, experiments were carried out. As a result, the improved surface quality of multi-track cladding can be obtained by judging the maximum waviness contour value. Based on the results of this study, a set of forming parameters database from single-track to multi-track cladding is provided for direct laser deposition.

論文審定書 i
誌謝 ii
摘要 iii
Abstract iv
目錄 v
圖次 viii
表次 x
符號表 xii
第一章 緒論 1
1.1前言 1
1.2文獻回顧 1
1.3研究目的與研究方法 4
1.4論文架構 5
第二章 直接式能量沉積與二極體雷射 6
2.1 直接式能量沉積法 6
2.1.1 直接式能量沉積法製程介紹與比較 7
2.1.2 直接式雷射沉積加工參數 9
2.2 雷射光學與二極體雷射 10
2.2.1 雷射光學特性 10
2.2.2光束品質 13
2.2.3應用雷射源比較 14
第三章 實驗方法 16
3.1 田口法介紹 16
3.1.1 直交表 17
3.1.2 訊號雜訊比 19
3.1.3 反應表與反應圖 20
3.2 實驗流程 21
3.3 實驗材料與設備 23
3.3.1 實驗材料 23
3.3.2 實驗設備 24
3.4 單道熔覆實驗設計與試驗 27
3.4.1單道熔覆L8交互作用實驗 28
3.4.2測試階段單道熔覆L9實驗 30
3.4.3優化階段單道熔覆L9實驗 32
3.5 同功率不同掃掠速率之熔覆寬度實驗 34
3.5.1多道熔覆試驗 35
3.6 試片量測 36
3.6.1 單道熔覆層量測 36
3.6.2 多道熔覆層量測 37
第四章 熔覆層幾何分析 38
4.1 單道熔覆L8交互作用分析 38
4.2 測試階段單道熔覆L9實驗分析 43
4.3 優化階段單道熔覆L9實驗分析 47
4.4 同功率不同掃掠速率之熔覆寬度分析 50
4.5 多道熔覆之重疊率實驗分析 55
第五章 結論 67
參考文獻 68

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