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為了降低鎳基超合金René 77在傳統TIG銲接時易銲接熱裂的特性，因此本研究採用低功率之脈衝式Nd:YAG固態雷射並搭配René 41銲線進行銲補，並設計一系列之銲補條件(三種銲接電壓及不同銲補挖槽)，觀察其金相微結構與機械性質的變化，藉以了解破裂機制；另外，本研究亦以傳統TIG銲接方式，以業界提供最佳化之銲接條件進行一組試片的銲接，並探討TIG與Nd:YAG雷射銲接微組織及機械性質的差異性。
實驗結果以金相觀點顯示，因雷射銲接的扭曲變形量較小形成較窄銲道，造成銲道內晶粒以柱狀晶與胞狀晶(Cellular)為主；而熱影響區因雷射高能量密度的關係，使銲道周圍γ’相因承受較快銲接熱循環(Thermal Cycle)導致熱影響區極窄，僅有小區域γ’相晶粒有粗化的現象。而氬銲TIG高功率之特性造成較寬熔池，因此在TIG銲道內部晶粒可觀察到柱狀、樹枝狀晶及等軸樹枝狀晶等；而熱影響區在較大熱輸入量與扭曲變形相對較寬，可被細分成三個區域分別為完全固溶區(Full of Reversion γ’)、部分固溶區(Partial of Reversion γ’)與γ’相晶粒粗化(γ’ Grains Growth)等區域。
就破裂而言，若雷射銲補的預挖凹槽深度越深，伴隨銲接電壓增加，所引發殘留應力較高導致銲道凝固裂縫的可能性也增加；且在銲道搭疊比例過大造成重熔比例增加，容易造成熱影響區由γ’相、碳化物與(γ+γ’)共晶相所引起的熔析裂縫等問題。在氬銲TIG銲接後無裂縫的產生，但TIG銲接產生較大扭曲變形與殘留應力，導致氬銲TIG的硬度值高於Nd:YAG雷射銲接，因此在後續熱處理容易導致時效應變裂縫的可能性。
經由上述金相與破裂結果顯示，若René 77鎳基超合金能選用合適的銲接方式、銲接能量及挖槽方式，將可降低Nd:YAG銲補後凝固裂縫與熔析裂縫。

To eliminate cracks of René 77 nickel base superalloy welds caused by high energy input of the traditional TIG (Tungsten Inert Gas) process, a low power and pulsed welding technique, Nd:YAG laser welding (LW) with René 41 welding wires, was used in this study. A series of laser welding parameters (including various energy inputs and grove designs) were applied to investigate their microstructure development and find out their possible crack mechanism. Moreover, a weld without crack produced by TIG welding process was studied to compare its microstructure and mechanical property with the welds produced by Nd:YAG LW process.
Microstructure investigations were shown, due to its nature of high energy density and low energy input, the Nd:YAG LW resulted in less distortion, and formed the narrow weld zone and HAZ. Across the weld, the solidification modes were columnar and cellular. In the heat affected zone (HAZ) the γ '' phase only have the coarsening phenomenon, the γ'' reversion was not obviously. But for TIG welding process, due to its lower energy density and higher energy input, the great distortion, and the wider weld fusion zone (WFZ) and HAZ were formed. The solidification mode in the WFS changes from columnar to dendrite and equiaxed dendrite. In the HAZ, reversion of γ'' ranges were the γ'' full reversion near the fusion line, the γ'' partial reversion in the middle of the HAZ and γ'' grain coarsening area near the edge of the HAZ.
The cracking behaviors of the Nd:YAG LW were shown, if the groove depth, reheated volume of as-deposited weld or energy input were increased, which provided the higher restrain stress in the weld, the solidification crack in the WFS more likely occurred. Besides crack in the weld, if the reheated volume of as-deposited weld was increased, liquation crack in HAZ by γ'', carbides and eutectic(γ-γ’) more liable occurred.
For TIG welds, despite there was crack-free in WFS and HAZ, however, due to the great distortion and residual stress, the Strain-age crack after post welding heat treatment may occur.

中文摘要I
英文摘要III
誌謝IV
總目錄V
表目錄VII
圖目錄VIII
第一章 前言1
第二章 文獻回顧3
2-1 鎳基超合金3
2-2 René 77鎳基超合金15
2-2-1 René 77之銲接特性19
2-3 銲接熱裂21
2-3-1 凝固裂縫(Solidification Cracking)21
2-3-2 熔析裂縫(Liquation Cracking)22
2-4 氬銲TIG銲接28
2-5 雷射銲接(Laser Welding)30
第三章 實驗方法34
3-1 實驗流程34
3-2 Nd:YAG雷射銲接參數37
3-3 氬銲TIG銲接參數41
3-4 René 41銲線42
3-5 René 77試片設計與製備43
3-6 金相觀察46
3-7 XRD成份分析47
3-8 機械性質測試48
第四章 結果與討論49
4-1 René 77基材之觀察49
4-2 Nd:YAG雷射及氬銲TIG銲補後微結構之觀察52
4-3 Nd:YAG雷射銲補後銲道微結構之觀察54
4-3-1 Nd:YAG雷射銲補後熱影響區微結構之觀察62
4-3-2 Nd:YAG雷射銲補後銲道XRD結晶構造分析67
4-4 氬銲TIG銲補後銲道顯微結構之觀察69
4-4-1 氬銲TIG熱影響區微結構之觀察73
4-5 Nd:YAG雷射及氬銲TIG銲補後破裂缺陷之觀察79
4-5-1 Nd:YAG雷射預挖凹槽及雷射走銲之破裂缺陷觀察79
4-5-2 TIG銲補後裂縫缺陷之觀察98
4-6 Nd:YAG雷射及氬銲TIG銲補後硬度值之比較99
第五章 結論101
參考文獻101
作者簡介107
表2-1 超合金中所添加之元素6
表2-2 René 77 之化學組成20
表2-3 高溫裂縫之分類24
表3-1 René 77鑄件雷射銲接參數與銲接狀況分析表38
表3-2 本實驗使用脈衝式固態雷射銲接參數38
表3-3 本實驗使用氬銲TIG銲接參數40
表3-4 René 41 之化學組成41
表4-1 TiC碳化物之EDS成份表49
表4-2 穿越銲道TiC碳化物之EDS成份表60
表4-3 氬銲TIG銲道內析出之TiC碳化物成份表71
表4-4 TiC碳化物之成份表97
圖2-1 超合金高溫下抗應力破裂及溫度使用範圍4
圖2-2 超合金在高溫下經1000h應力強度性質之比較(a)鐵基；(b)鎳基及(c)鈷基5
圖2-3 鎳基超合金顯微組織:(a)主要相組成；(b)有害相11
圗2-4 ㄧ般鎳基超合金重要的組成元素12
圖2-5 鈦、鋁含量對鎳基超合金之強度影響13
圖2-6 γ’析出相變化之外觀形狀趨勢13
圖2-7 鎳基超合金中有害相TCP之σ相14
圖2-8 TCP之σ相影響材料之應力破裂壽命14
圖2-9 差排通過γ''相顆粒之兩種機構17
圖2-10 APB反相界面示意圖18
圖2-11 各種合金元素常溫下對鎳基超合金降伏強度之影響18
圖2-12 鎳基超合金鈦、鋁含量對其銲接性之影響20
圖2-13 熱裂發生溫度24
圖2-14 銲道經常發生的凝固裂縫(Solidification Cracking)25
圖2-15 凝固裂縫之示意圖25
圖2-16 熱影響區的熔析裂縫(Liquation Cracking)發生區域(標示為A)26
圖2-17 液化裂縫之示意圖26
圖2-18 鋁合金五種液化現象之發生機制:(a)相圖；(b)三種機制低於溶質溶解度(CSM)；(c)二種機制超過溶質溶解度(CSM)27
圖2-19 氬銲TIG銲接示意圖29
圖2-20 雷射光之基本原理31
圖2-21 CO2 (Gas)雷射構造示意圖32
圖2-22 Nd:YAG (Solid State)雷射銲接示意圖33
圖3-1 本實驗鎳基超合金René 77銲補研究之流程圖35
圗3-2 本實驗所設計之半自動化台車36
圖3-3 本實驗所使用脈衝式Nd:YAG固態雷射銲補機及銲接專業人員39
圖3-4 本實驗使用René 77之示意圖42
圗3-5 (a)本實驗所設計銲接的預挖凹槽與表面走銲(Bead-on-plate)試片示 意圖；(b)試片銲接後之剖面圖43
圖3-6 René 77經Nd:YAG雷射(a)預挖凹槽(b)表面走銲與(c)氬銲TIG之銲補後試片外觀44
圖3-7 Hitachi-4700場發射掃描式電子顯微鏡45
圖3-8 本實驗所使用X光繞射儀機46
圖3-9 Nd:YAG(a)與氬銲TIG(b)之硬度測試示意圖47
圖4-1 René 77經鑄造後(a)γ及γ’相微組織；(b)TiC碳化物及(c)共晶相49
圖4-2 René 77之As-cast 1與As-cast 2金相觀察與硬度值測試50
圖4-3 Nd:YAG雷射銲接後經高倍SEM觀察單道多層銲道內部示意52
圖4-4 氬銲TIG銲接後經OM觀察單道多層銲道內部示意圖52
圗4-5 René 77經雷射銲補後(a)銲道中心之網狀結構；(b)網狀結構內 100,000倍所觀察參雜γ與γ’相結晶相55
圗4-6 René 77經雷射後銲道周圍晶粒<100>方式成長56
圗4-7 René 77經雷射銲補後銲道中心與<100>成長方向交錯56
圗4-8 René 77經雷射後銲道表面之微組織57
圗4-9 René 77經雷射後銲道之重熔區57
圖4-10 René 77之未均勻互融區EDS Linescan之Mo成份圖58
圖4-11 René 77經Nd:YAG銲接電壓170V(a)、180V(b)及190V(c)雷射銲接後產生未均勻互融區59
圗4-12 穿越銲道之連續式TiC碳化物60
圗4-13 René 77經銲接後銲道搭疊區之γ’晶粒產生粗大現象62
圗4-14 René 77經銲接電壓170V(a)、180V(c)、190V(e)雷射銲補後銲道周圍受到熱影響之粗化γ’相；而銲接電壓170V(b)、180V(d)、190V(f)雷射銲補後銲道周圍未受到熱影響之γ’相63
圖4-15 René 77經Nd:YAG預挖凹槽170V(a)、180V(c)、190V(e)與表面走銲170V(b)、180V(d)、190V(f)銲補後之母材熱影響區γ’相比較64
圗4-16 René 77經銲接電壓200V雷射銲補後受到嚴重熱影響之母材γ’相65
圖4-17 René 77經Nd:YAG雷射銲接電壓170V、180V及190V的銲道與René 77母材的XRD圖67
圗4-18 René 77經TIG銲補後銲道底部之柱狀晶69
圗4-19 René 77經TIG銲補後Linescan檢測銲道與母材底部產生互融現象69
圗4-20 René 77經TIG銲補後銲道中心之樹枝狀晶70
圗4-21 René 77經TIG銲補後銲道表面與銲道中心之等軸樹枝狀晶70
圗4-22 René 77經TIG銲補後銲道內部析出之碳化物71
圗4-23 René 77經TIG銲補後與銲道René 41互融之熱影響區74
圗4-24 René 77經TIG銲補後銲道重融區之柱狀晶74
圗4-25 René 77經TIG銲補後與銲道RENE 41互融的熱影響區(a)熱影響區之示意圖；(b)重熔後大量二次析出γ’ 相；(c)殘留未固溶γ’相 及少量二次析出γ’相； (d)受到熱影響之晶粒粗化γ’ 相；(e)未受到熱影響之γ’相(磷酸腐蝕液)75
圗4-26 René 77經TIG銲補後之銲道與完全固溶區之Linescan76
圗4-27 René 77經TIG銲補後與銲道René 41互融的熱影響區(a)未受到熱影響之γ’相；(b)重熔後大量二次析出γ’相(Marble腐蝕液) 77
圖4-28 (a) René 77經Nd:YAG銲接電壓190V的預挖凹槽與雷射走銲產生破裂之比較圖81
圖4-28 (b) René 77經Nd:YAG銲接電壓180V的預挖凹槽與雷射走銲 產生破裂之比較圖82
圖4-28 (c) René 77經Nd:YAG銲接電壓170V的預挖凹槽與雷射走銲 產生破裂之比較圖83
圗4-29 預挖凹槽René 77經Nd:YAG銲接電壓170V(a)、180V(b)及190V(c)銲補後銲道內部產生沿晶破裂形貌84
圗4-30 預挖凹槽René 77經Nd:YAG銲接電壓190V銲補後之結果(a)銲道內部搭疊處產生破裂；(b)搭疊處因晶粒成長方向不同所 產生沿晶破裂85
圖4-31 銲接凝固後之形狀影響表面之應力86
圗4-32 預挖凹槽René 77經Nd:YAG銲接電壓190V、180V及170V銲補後銲道尾端凝固凹型銲接面產生凝固裂縫87
圖4-33 René 77經Nd:YAG雷射銲補後產生液化裂縫之示意圖(a)銲補後產生液態薄膜；(b) 液態薄膜經凝固後產生液化裂縫；(c)導致熔析裂縫過程重複(a)、(b)92
圗4-34 René 77經Nd:YAG銲接電壓170V(a)、180V(b)及190V(c)銲補後由γ’相液化所產生熱影響區裂縫93
圖4-35 René 77經Nd:YAG銲接電壓200V銲補後在遠離銲道周圍所觀察到微縫94
圖4-36 René 77經Nd:YAG(a)銲接電壓170V銲補後未產生由(γ+γ’)共晶相所引起裂縫；銲接電壓180V銲補後由(γ+γ’)共晶相所引起穿越銲道之裂縫95
圗4-37 René 77經Nd:YAG銲接電壓170V(a)、180V(b)及190V(c)銲補後產生連續TiC碳化物穿越未均勻混合區域96
圗4-38 René 77經Nd:YAG銲接電壓180V銲補後由TiC碳化物所產生 熱影響區裂縫97
圖4-39 René 77經氬銲TIG銲接後無觀察到裂縫產生98
圖4-40 René 77經Nd:YAG雷射與氬銲TIG銲接後之硬度比較值100
圖4-41 René 77經Nd:YAG雷射(a)與氬銲TIG(b)銲補後銲道內之γ’相晶粒100

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