選擇性雷射熔融(SLM)製造為積層製造的重要方法之一，對於金屬零件的原型製作或形貌複雜工件的製作，較傳統製程有明顯的加工優勢。本計畫將延續目前執行的計畫(MOST 108-2221-E-008-098)，以具有優異性能且用途廣泛的鎳基超合金Inconel 718為對象，製作SLM試片，進行疲勞測試與分析。探討在最佳SLM製程及熱處理條件下，其金相組織、疲勞性質及破壞機構間之因果關係。全程計畫為兩年，第一年探討無裂縫的SLM工件的高週疲勞性質及應力-壽命法疲勞壽命評估模式。建立在不同應力比值的等振幅負荷下之疲勞性質資料、平均應力修正模式，並利用變動振幅負荷歷程的實驗結果來發展最佳的高週疲勞壽命評估模式。第二年利用破壞力學方式探討具有裂縫的SLM工件之疲勞裂縫成長速率及疲勞裂縫延伸壽命分析方法。經由實驗與理論預測結果之比較，以瞭解不同疲勞裂縫成長評估模式之適用性及準確性。在工件無裂縫或具有裂縫時，前述兩種疲勞分析及設計觀點可相輔相成，構成完整的疲勞分析系統。此外，本計畫亦將探討此種工件的疲勞裂縫起始及裂縫成長機制。本研究預期可建立Inconel 718合金SLM工件之疲勞性質及適用的疲勞壽命評估模式，解決其耐久疲勞設計上的問題，供未來使用相關製程與材料的人員作參考。研究成果將具學術及應用價值，並可提升鎳基超合金在國防及航太等工業上的應用。 ;Selective laser melting (SLM) manufacturing is one of the important methods in additive manufacturing. Obviously, SLM has processing advantages over traditional manufacturing processes in prototyping of metal parts or manufacturing of complex shaped parts. This project will continue the plan currently implemented (MOST 108-2221-E-008-098) with Inconel 718 produced by selective laser melting as the target. The tests and analyses of SLM Inconel 718 specimens will be performed to explore the causal relationship between microstructure, fatigue property and failure mechanism. This is a two-year project. In the first year, we will investigate high cycle fatigue properties and stress-life (S-N) fatigue life evaluation model of SLM Inconel 718 specimen. The mean stress correction model in fatigue analysis will be established. The optimal high fatigue life evaluation model will be developed based on the experimental results of variable amplitude fatigue test. In the second year, the fatigue crack growth rate and the residual life estimation of a cracked SLM Inconel 718 specimen were studied by means of fracture mechanics. The mechanisms of fatigue crack initiation and fatigue crack propagation will be discussed. The proposed fatigue life evaluation model will be helpful for solving fatigue design issues of SLM Inconel 718 alloy. The results of this project will be of academic and practical value, and also enhance the industrial application of nickel-based superalloys.
