總結 22Cr-25Ni-xNb 不銹鋼顯微組織

表 4.3.5.1 中，可以發現，在不同 Nb 含量為(0、0.29、0.58、0.86wt%) 的試片，共有三種析出相，分別是析出在基地的γ 相、析出在晶界上的 M₂₃C6

以及析出在晶界上及晶粒內的 Nb(C,N)相；M₂₃C6析出形貌為樹枝狀、網狀、

羽毛狀、長條塊狀，而 Nb(C,N)析出形貌為細長狀棒狀及橢圓狀；而隨著 Nb 含量的增加，M23C6及 Nb(C,N)析出形貌越趨近於不規則。

根據 B.Sasmal^[43]文獻，試片在熱處理過程中有未溶解 NbC 顆粒時，會 影 響 周 圍 的 M₂₃C6 析 出 ， 析 出 形 貌 為 六 邊 矩 形 板 狀 ； 而 22Cr-25Ni-3W-3Cu-1.5Co-xNb 不銹鋼試片，固溶處理條件是 1300℃、2 小 時，根據^[30]文獻，Nb(C,N)相的溶解溫度為 1311℃，所以試片在固溶處理 後，會有未溶解的 NbC 顆粒析出在晶粒內；已得知未溶解的 NbC 顆粒會

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去影響周圍的 M₂₃C6析出形貌；而在熱處理過程中析出的 Nb(C,N)相也會影 響 M₂₃C6相的析出形貌，由 4.3.2 顯微組織的結果得知；由於 Nb 元素的添 加，會使 M₂₃C6及 Nb(C,N)析出相，彼此互相影響析出形貌，而使析出形貌 變得複雜，所以在後面的章節，不討論含 Nb 的 22Cr-25Ni-3W-3Cu-1.5Co -xNb 不銹鋼試片析出形貌，我們只探討 Nb 含量 0wt%不銹鋼試片的析出形 貌，其析出相只有 M₂₃C6相。

由於 22Cr-25Ni-3W-3Cu-1.5Co -xNb 不銹鋼試片時效熱處理 (700℃、

1000 小時時效內)，Z 相的析出量極少^[42]，而我們利用掃描式電子顯微鏡觀

表 4.3.5.1 總結 22Cr-25Ni-3W-3Cu-1.5Co -xNb 沃斯田鐵系不銹鋼，不同 Nb 含量(0、0.29、0.58、0.86wt%)顯微組織觀察的結果。

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貌的晶界；最後爐冷至 300℃、爐冷的時間為 5 小時 21 分鐘 49 秒，如圖 4.4.1.2 (b)中顯示，發現在晶界處的 M23C6析出量變多，其開始有不同析出 形貌產生。

圖 4.4.1.1 為溫度-時間之爐冷曲線圖

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圖 4.4.1.2 SEM 影像觀察，爐冷至(a)800、(b)500、(c)300℃後水淬之顯微形 貌

4.4.2 連續冷卻變態圖

由圖 4.4.2.1 中，爐冷至 800℃時，M₂₃C6在晶界上析出的形貌有兩中類 型如圖(a)、(b)；可以觀察到，在一些晶界區域如圖 4.4.2.1(a)沒有 M₂₃C6析 出，而(b)圖中則有非常少量的 M₂₃C6在晶界上析出，所以可以推測，M₂₃C6

開始析出的爐冷溫度為 800℃。

將圖 4.4.1.1 為溫度-時間之爐冷曲線圖，X 軸(時間)取 10 的對數，而形 成如圖 4.4.2.2 連續冷卻變態曲線(CCT 圖)；由上述已知在 800℃時已有 M23C6開始析出，其析出量非常少；所以可以大略的畫出，M₂₃C6開始析出 的曲線(C 曲線的上半部份)，如圖 4.4.2.2 中紅色曲線，曲線大略在 800℃的 上方。

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圖 4.4.2.1 SEM 影像觀察，爐冷至 800℃後水淬之顯微形貌

圖 4.4.2.2 連續冷卻變態曲線(CCT 圖)

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99

圖 4.4.3.1 比較固溶處理後分別爐冷至 500、300℃後水淬，利用 SEM 來觀 察 M₂₃C6在晶界析出的顯微形貌。

4.4.2 共位晶界對 M

23

C

6

相於晶界上析出之影響

共位晶界為經由共位晶格點組成之晶界稱之，共位晶格點位置所組成之 晶界屬“大角度”晶界，根據 V. Randle^[20]文獻指出，共位晶格模型為個別晶 界取向差以Σ 值代表。在 2.4 章節，根據 S.W. Nam ^[19]文獻指出，共位晶界

100

101

相，而根據 Howell et al. ^[67]文獻指出，在 20Cr-25Ni 沃斯田鐵系不銹鋼中，

共位晶界的比例可能會高達 78％；而根據上述文獻結果，共位晶界 Σ 值的 不同，會有不同的 M₂₃C6析出形貌；所以我們知道，M₂₃C6在晶界上會析出 樹枝狀、網狀、羽毛狀及長條塊狀等形貌，至少有兩個因素會影響，其中 之一為爐冷，爐冷過程使晶界上析出大量的 M₂₃C6，晶界上差排密度降低，

而影響 M₂₃C6的析出形貌，另一個則是晶界上的取向差共位晶格的 Σ 值，

會有不同的 M₂₃C6析出形貌。

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結論

1. 藉 由 X-ray 及 SEM-EDS 分 析 結 果 ， 發 現 鈮 含 量 為 0 wt% 之 22Cr-25Ni-3W-3Cu-1.5Co-xNb 不銹鋼中，析出 M23C6相，而隨著鈮含量 增加至(0.29wt%、0.58wt%、0.86wt%)時，發現除了有 M₂₃C6析出相之 外，還有 Nb(C,N)、Z 相析出；而在不同鈮含量(0wt%、0.29wt%、0.58wt%、

0.86wt%)，700℃、時效 1000 小時的試片中，並沒有發現新的析出相產 生。

2. 22Cr-25Ni-3W-3Cu-1.5Co-xNb 不銹鋼試片隨著 Nb 含量的增加，晶粒尺 寸變得越小。另一方面，之鈮含量為 0wt%時，在晶界上析出 M₂₃C6相，

3. 22Cr-25Ni-3W-3Cu-1.5Co-xNb 不銹鋼試片，隨著 Nb 含量的添加，在 晶界上的 M₂₃C6的析出量變少，析出形態為塊狀與樹枝狀，且 Nb(C,N) 在晶粒內析出時，會有團聚的現象產生。

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4. 由試驗結果得知，固溶處理後利用爐冷冷卻至 800、500、300℃後水淬，

觀察晶界上 M₂₃C6的析出形貌；爐冷至 800℃時，在晶界並沒有發現析 出相產生，且晶界為筆直的形狀；隨著爐冷至 500℃時，在晶界上開始 有 M₂₃C6相析出；最後爐冷至 300℃，在晶界處的 M₂₃C6析出量變多，

且開始有不同析出形貌產生。

104

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在文檔中 時效處理對22Cr-25Ni-3W-3Cu-1.5Co-xNb不銹鋼顯微組織影響之研究 (頁 104-0)