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The Cavitation Behavior of Inconel 690 Alloy
Hao, Chen Jie
|關鍵字:||Inconel 690 alloy;Inconel 690合金;cavitation;TiN;窩蝕;氮化鈦||出版社:||材料工程學研究所||摘要:||
Inconel 690合金是現今工業界中用於高抗蝕性、高強度需求的環境中，相當重要的構件材料之一。然而在以Inconel 690合金為構件材料的設備中，除了有發生應力腐蝕(SCC)以及粒界應力腐蝕(IGSCC)之虞，窩蝕(cavitation)所造成的破壞也扮演著相當重要的角色，本研究便是針對Inconel 690合金的窩蝕(cavitation)破壞現象作一定點的連續觀察，進行窩蝕試驗前，先藉由金相試驗、硬度量測、X-ray繞射等鑑定分析Inconel 690合金之顯微組織及基本性質，而後進行窩蝕試驗，並針對晶界、雙晶、析出物等位置作定位，每隔一固定的時間連續觀察其受窩蝕破壞的情形，了解Inconel 690合金的窩蝕破壞機構。
實驗結果顯示Inconel 690合金的窩蝕破壞起始於晶界、雙晶、及析出物與基材之界面，此外亦有孔蝕( Pitting)的發生，實驗也發現在窩蝕初期有加工硬化現象發生。而對照其窩蝕破壞的階段可以發現在潛伏期階段(incubation period)主要是小尺寸的氮化鈦析出物破壞剝落、孔蝕產生的小坑穴及晶界處塑性變形的小區塊剝落，因此造成的材料損失率很小，但隨著窩蝕時間的增加，潛伏期階段產生之小坑穴逐漸擴大損失的區域，進入加速期(acceleration period)後，破壞的形式變成是大的坑穴相互連結使材料呈塊狀剝落，造成加速期大量材料的流失。此外，析出物的尺寸大小對其抗窩蝕性亦有所影響，過大或過小的尺寸在潛伏期便會遭破壞，存在一適當的析出物尺寸對抗窩蝕性有最佳的效果。
Inconel 690 alloy is an important material which is used in environment that needs high erosion resistance and high strength. However , in some equipments that use Inconel 690 alloy as components, besides SCC and IGSCC phenomenon exist, the fracture that made by cavitation was also plays an important role. This research concerns about the cavitation behavior of Inconel 690 alloy. Before the experiment of cavitation, the metallographic analysis, the hardness, and X-ray diffraction to analyze and identify the microstructure and quality of the bases of Inconel 690 alloy. Next, begining to do the cavitation test, first of all, need make a spot on grain of the boundary, twin boundary, and educt. During the experiment, the condition of cavitation behavior was observed over and over again to understand the mechanism of the cavitation of Inconel 690 alloy.The result shows that cavitation fracture of Inconel 690 alloy occurrs initially at grain boundary, twin, and interface between precipitate and matrix. Besides, pitting also occurrs. The study also finds that work-hardening occurred in the initial stage of cavitation. Comparing to each periods of cavitation, The causes of weight lost in incubation period was the small TiN precipitations come off and the lost of deformation area at grain boundary and twin boundary, the loss ratio was very lightly. But with increasing time of cavitation, the little pits that produced in incubation period became larger. When it come to acceleration period, the causes of weight lost was the big holes mixed together so that to result big pieces lost of material. In addition, the particle size of precipitations is an important factor for cavitation resistance during incubation period. It has a appropriate particle size that has high resistance to cavitation .
|Appears in Collections:||材料科學與工程學系|
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