Incoloy800H之超合金板料在市場上佔有率大，主要應用在石化系統的管件、熱交換器、加熱爐內部組件、鍋爐及壓力容器 [1]，也是未來第五代核電廠選用的材料之ㄧ [2]。近年來鈦、鎳、銅等超合金元素之價格高漲，欲致力於降低原料成本可藉由合金設計與在不改變成分的狀態下利用晶界工程來開發高經濟效益的合金[3]。Incoloy800H為沃斯田鐵系固溶強化型之超合金，成分組成以鐵-鎳-鉻為主，其他元素的添加如銅、矽、錳、鋁、鈦、碳，因此材料組織含有碳化鉻、碳化鈦 [4]。晶界工程, Grain boundary engineering (GBE)為將原始晶界的型態或本質改良已達到強化晶界之功法，藉由熱機處理來控制Grain boundary character distribution (GBCD)以及製造出高比率的特殊晶界 (special boundary) [5]，特殊晶界具有相對低的晶界能[6]，使得沿晶破裂、氧化、腐蝕、偏析的可能性降低 [7-15]，同時增進多晶材料中延性破裂強度。晶界工程特別適合低疊差能的金屬材料，如銅、鎳等等，故800H非常適合利用GBE來提升合金效能。特殊晶界，尤其是Σ3的晶界能為最低 [16]，最有利於晶界之改質，但熱機處理後，產生之Σ3多為退火雙晶，此雙晶界包含在晶粒內，對晶粒間晶界無貢獻，故須藉由多道次的熱機處理使Σ3反應生成非雙晶型之Σ3。除了提升特殊晶界量外，其特殊晶界之分佈位置亦為一重點，晶界交叉之Triple Junctions上可能產生零至三個特殊晶界，分別標為J0、J1、J2、J3(圖 1)，若產生最多量的J2，將有助於各項合金性質的提升 [17]。

Contents
Abstract 3
I. Introduction 5
II. Literature review 8
2.1 INCOLOY 800H 8
2.2 Special boundaries 8
2.3 Property improvements by GBE 11
III. Experiments 14
3.1 Material 15
3.2 Solution heat treatment (SHT) 15
3.3 Differential scanning calorimetry (DSC) analysis 15
3.4 The grain boundary engineering (GBE) process 17
3.5 X-ray diffractometer 19
3.6 Optical metallography 19
3.7 Scanning electron microscopy 19
3.8 Electron Backscatter Diffraction (EBSD) 19
3.9 Special boundary analysis 20
3.10 Oxidation test 21
3.11 Sensitization test 21
3.12 Creep test 22
3.13 High temperature tensile test 23
IV. Results and discussion 24
4.1 Microstructures prior GBE processes 24
4.2 GBCD of preliminary GBE process (route-1) 26
4.3 Oxidation test 31
4.3.1 982℃ oxidation tests 32
4.3.2 900℃ oxidation tests 32
4.4 Sensitization test 38
4.5 Creep test 40
4.6 High temperature tensile test 44
4.7 Further GBE processes: effect of grain size and twin density 46
V. Conclusion 58
VI. Future work 60
References 61

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