| 摘要註: |
本研究以燃煤火力發電廠過熱管用之22Cr-25Ni-3W-3Cu-1.5Co-xNb耐熱不銹鋼(SanicroR25)為實驗材料，實驗分為三部份，第一部份主要探討鈮含量為(0 wt%、0.29 wt%、0.58 wt%、0.86 wt%)時，在時效溫度700℃及時效（10、100、1000小時)之相鑑定結果，而第二部份則探討鈮的添加量(0 wt%、0.29 wt%、0.58 wt%、0.86 wt%)對顯微組織之影響，最後第三部份則探討鈮含量為0 wt%時，未熱處理之試片的M23C6碳化物在晶界上析出形貌之研究。從第一部份的實驗結果得知22Cr-25Ni-3W-3Cu-1.5Co-xNb 不銹鋼中，鈮含量為0 wt%時，有M23C6相析出，隨著鈮元素的添加使不銹鋼中新析出Nb(C,N)、Z(CrNbN)相；在700℃，時效1000小時的試片中並沒有發現新的析出相產生。另外從第二部份的實驗結果得知，在不同鈮含量為(0 wt%、0.29 wt%、0.58 wt%、0.86 wt%)時之顯微組織觀察結果；首先我們發現Nb(C,N)碳氮化物；鈮含量為0 wt%、0.29 wt%，Nb(C,N) 碳氮化物形貌為細小的棒狀、橢圓狀在晶界上及晶粒內析出，隨Nb含量增加至0.58 wt%、0.86 wt%時， Nb(C,N)析出相變得粗大且趨向不規則狀；隨著Nb含量的增加，晶粒尺寸變得越小。且發現在不同鈮含量為(0 wt%、0.29 wt%、0.58 wt%、0.86 wt%)時，析出Nb(C,N)碳氮化物均有團聚的現象。接著我們來討論M23C6碳化物析出形貌，在鈮含量為0 wt%時，在晶界上析出M23C6相，其形貌有樹枝狀、網狀、羽毛狀、長條塊狀，而隨著Nb含量增加至0.29 wt%、0.58 wt%，在晶界上M23C6析出相 (樹枝狀、羽毛狀、網狀)變少，但是在0.86Nb時，M23C6析出相(樹枝狀、羽毛狀、網狀)卻又增加；且析出形貌為M23C6（樹枝狀+羽毛狀+網狀）+ Nb(C,N)（橢圓狀）。最後從第三部份的實驗結果得知，固溶處理(1300℃、持溫2小時)後爐冷，爐冷由1300℃至800℃、600℃、500℃之後水淬，使得晶界上的M23C6析出的量變多。 This study is focused on a 22Cr-25Ni-3W-3Cu-1.5Co-xNb heat-resistant steel used as superheater and reheats for pulverized coal fired steam boiler. Experiment was divided into three parts, the first part focuses on the effects of added amount of niobium (0 wt.%, 0.29wt.%, 0.58wt.% ,0.86wt.%) and annealing temperature 700℃ with annealing time(10、100、1000 hour) on the phase identification；the second part focuses on the effect of added amount of niobium (0wt.%,0.29wt.%, 0.58wt.% ,0.86wt.%) on the microstructure; the third part focuses on the effect of added amount of niobium 0wt.% on the M23C6 carbide precipitation morphology in the grain boundary of no heat treatment specimen. From the experimental results of the first part on the 22Cr-25Ni-3W-3Cu-1.5Co-xNb stainless steels, the added amount of niobium 0wt.% of M23C6 carbide precipitation, with the addition of niobium in the stainless steel freshly precipitated Nb (C, N) carbo-nitride and Z (CrNbN) phase. However, no new precipitation is found aged for 1000 hour at 700°C.From the experiments of the second part, the results showed that the effects of added amount of niobium (0 wt.%, 0.29wt.%, 0.58wt.% ,0.86wt.%) on the microstructure observation. The first, we found Nb (C, N) carbo-nitride. The added amount of niobium 0 wt.% and 0.29wt.%, the small rod-shaped and ellipse-shaped Nb (C, N) carbo-nitride observed at grain boundaries and inside grains. When the niobium content was increased to 0.58 wt% and 0.86 wt%, Nb (C, N) carbo-nitride precipitates tend to become coarse and irregular. With the increasing of the niobium content, the grain size became smaller. And the added amount of niobium (0 wt.%, 0.29wt.%, 0.58wt.% ,0.86wt.%), Nb (C, N) carbo-nitride had the reunion phenomenon. Next, we discuss M23C6 carbide morphology, the dendrite-like, block-like, feathery-like and network-like M23C6 carbide observed at grain boundaries while the added amount of niobium was 0wt.%. As the niobium content was increased to 0.29 wt% and 0.58 wt%, M23C6 carbide which had dendrite-like, feathery-like and network-like became less at the grain boundaries. In addition, the dendrite-like, feathery-like and network-like M23C6 carbide became increased at the grain boundaries on the 22Cr25NiWCoCu stainless steels with 0.86wt.% Nb. The precipitates morphology was M23C6 carbide (feathery-like, dendritic-like and network-like) and Nb (C, N) carbo-nitride (ellipse-shaped). Finally, from the experiments of the third part, the furnace cooling after solution treatment (1300℃、hold 2hr). A specimen is furnace cooled from 1300℃ to 800℃ ,500℃ ,300℃ after water quench let the amount of M23C6 carbide increase at the grain boundaries. |