臺灣博碩士論文加值系統

液相燒結是最有效提升粉末冶金成品緻密性及提升燒結速率的製程法，其中硼元素為最常添加於鐵基材料中作為促進液相燒結的元素，本研究將探討304L(Fe-18.45Cr-11.04Ni)不銹鋼粉中添加不同尺寸之純硼粉與硼化鐵粉至304L不銹鋼中使其皆具有0.6wt%硼含量，並使用不同燒結溫度參數(1250°C、1275°C、1300°C)觀察其顯微組織與燒結密度影響，以及熱處理後對其機械性質與腐蝕特性之影響。
實驗結果顯示，添加純硼粉尺寸分別為1.7 µm、2.9 µm、3.2 µm於304L中，當添加純硼尺寸為3.2 µm時有最高的燒結密度可有效促進液相燒結，經由熱分析結果可發現在燒結過程中添加純硼粉的液相形成於1245°C~1277°C的溫度區間，而添加硼化鐵粉的液相則形成於1239°C~1268°C的溫度區間。從顯微組織中可觀察到兩種粉末在晶界處有大量的共晶硼化物生成。304L添加B與Fe2B在經由1300°C燒結後的各別密度由6.91 g/cm3大幅度提升到7.65 g/cm3及7.48 g/cm3，孔隙率分別從14 vol%下降到2 vol%及3 vol%。
比較304L+B及304L+Fe2B之燒結密度、孔隙率等相關分析後，發現304L+B之性質皆較304L+Fe2B具有較優異的性質，因此將304L+B參數進行拉伸試驗，發現304L在硼的添加後可使其抗拉強度從264 MPa提高至451 MPa，伸長率可高達13%，進一步將304L+B進行600°C熱處理後，其抗拉強度可明顯提高至472 MPa，衝擊能從43 J提升至47 J，顯示304L+B經由熱處理後對於機械性質的提升與改善，但過高的熱處理溫度將導致從晶界處往基地相中固溶之共晶硼化物較多而對機械性質產生負面效益，因此經上述結果得知，在304L不銹鋼中添加純硼粉進行燒結後的效益較硼化鐵粉高，不僅能有效提高燒結密度，亦使得機械性質提高，經由600°C熱處理後可使304L+B具有更優異的機械性質。

Liquid phase sintering is an effective method to improve the densification of powder metallurgy products and increase the sintering rate. Boron is the most commonly added element in iron-based materials to promote liquid phase sintering. This study will explore 304L stainless steel (Fe-18.45Cr-11.04Ni) powder with different sizes of pure boron powder and iron boride powder. The boron content was controlled at 0.6 wt%. The effects of sintering temperature (1250°C, 1275°C, 1300°C) on the microstructure and sintering density and the influences of heat treatment on the mechanical properties and corrosion characteristics were studied.

The results show that the 3.2 μm pure boron size in 304L can attain the highest sintered density and promote liquid phase sintering among the different sizes of pure boron powder (1.7 μm, 2.9 μm, and 3.2 μm). The results of thermal analysis indicate the liquid phase can be found in a temperature range between 1245°C and 1277°C when pure boron powder is added. While iron boride powder is used, the liquid phase is formed in a temperature range between 1239°C and 1268°C. Moreover, a large amount of eutectic boride at grain boundaries can be observed according to the microstructural observation. After 1300°C sintering, adding B and Fe2B powders can sufficiently increase the sintered density of 304L from 6.91 g/cm3 to 7.65 g/cm3 and 7.48 g/cm3, respectively. The porosity is decreased from 14 vol% to 2 vol% and 3 vol%, respectively.
The 304L+B steel exhibits better performances than 304L+Fe2B by comparing the sintering density and porosity. Therefore, the tensile properties of 304L+B steel was carried out. The results show that the addition of boron in 304L increases the tensile strength from 264 MPa to 451 MPa, and the elongation can be as high as 13%.After heat treatment of 304L+B at 600°C, the tensile strength can be obviously increased to 472 MPa, and the impact energy can be increased from 43 J to 47 J. These findings show the positive influence of heat treatment on the mechanical properties of 304L+B steel. However, when the heat treatment temperature is too high, more eutectic boride at grain boundary could dissolve into the matrix and impair the mechanical properties. In conclusion, pure boron powder can assist in the liquid phase sintering of 304L stainless steel, and increases the sintering density and the mechanical properties. After heat treatment at 600°C, the mechanical properties of 304L+B steel can be slightly increased.

中文摘要 i
英文摘要 iii
目錄 v
表目錄 viii
圖目錄 ix
第一章 緒論 1
第二章 文獻回顧 3
2.1 粉末冶金簡介 3
2.2 不銹鋼之介紹 5
2.2.1 沃斯田鐵系不銹鋼 6
2.2.2 肥粒鐵系不銹鋼 6
2.2.3 麻田散鐵系不銹鋼 7
2.2.4 雙相不銹鋼 7
2.3 液相燒結 8
2.3.1 液相燒結的階段 8
2.4 孔隙率對粉末合金鋼之影響 9
2.4.1 緻密性 9
2.4.2 腐蝕性質的影響 12
2.4.3 機械性質的影響 15
2.5 硼元素之液相燒結 18
2.6 合金元素對含硼合金鋼之液相燒結的影響 23
2.6.1 鎳的效應 23
2.6.2 鉬的效應 26
2.6.3 鉻的效應 28
2.6.4 碳的效應 30
2.7 添加之硼粉尺寸對液相燒結的影響 36
第三章 實驗步驟 39
3.1 實驗設計 39
3.2 實驗流程 40
3.2.1 粉末特性 41
3.2.2 粉末混合與成形 46
3.2.3 燒結條件 47
3.3 燒結密度量測 48
3.4 顯微組織觀察 48
3.5 硼化物之元素分佈與定量分析 49
3.6 熱分析 49
3.7 硬度 49
3.8 動電位極化曲線 49
3.9 拉伸性質分析 50
3.10 衝擊分析 51
3.11 分析儀器 52
第四章 結果與討論 53
4.1 顯微組織 53
4.1.1 304L於各溫度燒結後之顯微組織 53
4.1.2 304L添加不同尺寸之B粉的顯微組織 54
4.1.3 304L添加不同尺寸之Fe2B粉的顯微組織 60
4.2 304L+B之硼化物元素分佈與定量分析 63
4.2.1 硼化物之元素分佈 63
4.2.2 硼化物之定量分析 66
4.3 DSC熱分析 67
4.4 燒結密度 69
4.5 孔隙率、孔洞圓形度之平均尺寸分析 72
4.6 硼化物之硬度分析 78
4.6.1 洛氏硬度 78
4.6.2 維氏硬度 80
4.7 熱處理對各性質之影響 83
4.7.1 密度 83
4.7.2 硼化物經熱處理後之顯微組織及孔隙率 84
4.7.3 熱處理對於共晶生成物之硼化物體積影響 89
4.7.4 硼化物硬度之影響 90
4.8 機械性質之性質分析 93
4.8.1 拉伸性質分析 93
4.8.2 衝擊試驗分析 102
4.9 腐蝕特性 106
4.10 304L+0.6B不同製程之機械性質比較 110
第五章 結論 112
參考文獻 114

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