【摘要】：鎳基單晶高溫合金作為一種具備高溫下抗蠕變、抗腐蝕、抗氧化等能力的金屬材料,被廣泛應(yīng)用于航空發(fā)動(dòng)機(jī)及地面燃?xì)廨啓C(jī)的熱端部件。前期研究表明,鎳基單晶高溫合金的微觀組織對(duì)其力學(xué)性能有著重要的影響,而少量C元素的添加及熱處理工藝對(duì)合金顯微組織有很大影響。因此,本文以含C的第三代鎳基單晶高溫合金DD90為研究對(duì)象,通過(guò)調(diào)整合金中微量C元素的含量及改變熱處理工藝,研究C含量對(duì)合金凝固路徑、凝固特征溫度、枝晶組織、共晶組織和碳化物相的影響。采用不同的熱處理工藝,研究不同熱處理工藝對(duì)合金顯微組織、共晶組織及γ'相的影響以及分析熱處理前后碳化物形態(tài)的演變。得到以下主要結(jié)論:1、合金中C元素的添加使得合金的液相線溫度、固相線溫度、碳化物溶解溫度和γ'相溶解溫度均有所降低。此外,合金的結(jié)晶溫度區(qū)間對(duì)C元素的敏感程度不高,隨C含量的增加,其變化幅度不大。2、C含量對(duì)合金的枝晶間距的影響不大。隨著C含量的增加,合金中共晶組織體積分?jǐn)?shù)呈降低趨勢(shì),碳化物相含量呈增加趨勢(shì)且其尺寸變大,同時(shí)C元素的添加對(duì)合金γ'相的分布、尺寸和形貌沒(méi)有明顯影響。C含量低的合金其碳化物呈顆粒狀或塊狀;當(dāng)含C量較高時(shí),碳化物呈漢字體狀。3、由于C元素的添加,使得合金凝固特征溫度降低。經(jīng)相同熱處理后的不同C含量合金,其C含量越高的合金其枝晶消失程度越高。同時(shí),隨著C含量的增加,合金枝晶溶解越完全,共晶消除程度越高。且隨C含量的增加,合金熱處理態(tài)γ相尺寸隨之增大,γ'相數(shù)量逐漸減少。4、合金經(jīng)不同制度的熱處理后,均實(shí)現(xiàn)合金成分均勻化的目的,且偏析程度顯著降低。此外,隨著熱處理溫度的升高,合金中枝晶組織的輪廓逐漸變得模糊。當(dāng)固溶溫度設(shè)定在1305℃及以上時(shí),合金的枝晶輪廓幾乎完全消失。在采取最高溫度為1305℃的多步熱處理制度后,該合金中的共晶組織含量最低,且合金的γ'相具有好的立方度,高體積分?jǐn)?shù)。5、合金經(jīng)熱處理后碳化物與鑄態(tài)碳化物成分基本一致,表明在熱處理過(guò)程中,碳化物僅發(fā)生分解,進(jìn)而使得碳化物尺寸變小且趨于彌散分布。多步固溶處理的熱處理為碳化物分解提供了足夠的時(shí)間,與鑄態(tài)碳化物相比,熱處理態(tài)碳化物尺寸減小;當(dāng)提高熱處理溫度時(shí),碳化物分解程度提高,合金中的碳化物形貌更為簡(jiǎn)單,且尺寸明顯減小,碳化物主要以細(xì)小顆粒狀彌散分布。
[Abstract]:As a kind of metal material with high temperature resistance to creep, corrosion and oxidation, nickel base single crystal superalloy is widely used in the hot end parts of aero-engine and ground gas turbine. The previous studies show that the microstructure of Ni-base single crystal superalloy has an important influence on its mechanical properties, while the addition of a small amount of C element and the heat treatment process have great influence on the microstructure of the alloy. Therefore, the effect of C content on solidification path, solidification characteristic temperature and dendrite structure of the third generation nickel base single crystal superalloy (DD90) was studied by adjusting the content of trace C in the alloy and changing the heat treatment process, so as to study the effect of C content on the solidification path, solidification characteristic temperature and dendrite structure of the alloy. Effect of eutectic structure and carbide phase. The effects of different heat treatment processes on the microstructure, eutectic structure and 緯 'phase of the alloy were studied, and the evolution of carbide morphology before and after heat treatment was analyzed. The main conclusions are as follows: 1. With the addition of C element in the alloy, the liquid phase line temperature, the solid phase line temperature, the carbide dissolution temperature and the 緯 'phase dissolution temperature are all decreased. In addition, the crystallization temperature range of the alloy is not sensitive to element C, and with the increase of the content of C, the extent of the change is not significant. The effect of the content of 2C on the dendrite spacing of the alloy is not significant. With the increase of C content, the volume fraction of eutectic microstructure decreases, the content of carbide phase increases and its size increases, and the distribution of 緯 'phase of alloy is affected by the addition of C element. The carbides of the alloys with low content of .C have no obvious effect on size and morphology, and the carbides are like Chinese characters when the content of C is high, and the solidification characteristic temperature of the alloys decreases because of the addition of C elements. After the same heat treatment, the higher the C content, the higher the degree of dendrite disappearance. At the same time, with the increase of C content, the more complete the dendrite dissolution, the higher the degree of eutectic elimination. With the increase of C content, the size of 緯 phase in heat-treated alloy increases, and the number of 緯 'phase decreases by .4.After heat treatment in different systems, the composition of the alloy is homogenized and the segregation degree is reduced significantly. In addition, with the increase of heat treatment temperature, the outline of dendritic structure in the alloy becomes blurred. When the solution temperature is set at 1305 鈩，

本文編號(hào)：2215050