發(fā)布時(shí)間：2018-07-26 15:19

【摘要】：隨著國(guó)內(nèi)航空發(fā)動(dòng)機(jī)產(chǎn)業(yè)的不斷發(fā)展,鎳基單晶高溫合金處在高速發(fā)展階段,現(xiàn)階段的單晶制備工藝也已經(jīng)相當(dāng)成熟。因此,對(duì)單晶合金在熱處理以及服役過(guò)程中進(jìn)行組織和性能研究更有實(shí)際應(yīng)用價(jià)值,這對(duì)提高合金性能,了解合金的高溫穩(wěn)定性和壽命預(yù)測(cè)有重要意義。此外,隨著氣膜冷卻技術(shù)在國(guó)內(nèi)單晶葉片上應(yīng)用,國(guó)內(nèi)渦輪發(fā)動(dòng)機(jī)的承溫能力得到進(jìn)一步上升,而對(duì)氣膜孔周?chē)跓崞谘h(huán)下裂紋萌生擴(kuò)展機(jī)制缺少研究和探索。本文主要研究國(guó)內(nèi)自主研發(fā)第二代鎳基單晶高溫合金DD5合金的熱處理過(guò)程中組織改善、性能提升,在高溫服役過(guò)程中組織演變,以及合金冷熱疲勞循環(huán)下圓孔周?chē)鸭y萌生擴(kuò)展情況。本文通過(guò)JMatPro和DSC曲線(xiàn)對(duì)DD5單晶高溫合金固溶處理的溫度范圍進(jìn)行確定,并分別對(duì)合金進(jìn)行固溶處理工藝和時(shí)效處理工藝后研究發(fā)現(xiàn):均勻化處理和高溫固溶處理均能顯著改善合金組織中的枝晶偏析現(xiàn)象;固溶處理后的冷卻方式影響γ’組織形態(tài),水冷則是析出100nm以下尺寸的γ’組織;爐冷后組織顯得異常粗大,尺寸超出600nm;空冷后的γ’顆粒均勻且有序排列。固溶處理空冷后合金的顯微硬度是465左右,比鑄態(tài)組織的硬度要高出120;而固溶處理水冷樣品的顯微硬度則最高。熱處理中的時(shí)效處理對(duì)合金中γ’的尺寸形貌進(jìn)一步的調(diào)整,研究過(guò)程中發(fā)現(xiàn)一次時(shí)效(高溫時(shí)效)的溫度過(guò)低時(shí),會(huì)出現(xiàn)圓形的γ’顆粒,呈現(xiàn)出不規(guī)則排列;當(dāng)溫度上升時(shí),則γ’顆粒逐漸呈立方態(tài)有序排列,從而獲得有序排列的立方γ’相;當(dāng)溫度繼續(xù)上升,標(biāo)準(zhǔn)的立方態(tài)的γ’相顆粒邊角鈍化。本文獲得DD5單晶高溫合金的最佳熱處理工藝為:1270℃,2h+1280℃,2h+1290℃,2h+1300℃,2h+1310℃,2h+1320℃,6h AC+1080℃/4h AC+780℃/24h AC。DD5單晶高溫合金在長(zhǎng)期時(shí)效實(shí)驗(yàn)中的研究表明:時(shí)效時(shí)間越長(zhǎng),γ’相越大,最終出現(xiàn)形筏現(xiàn)象;長(zhǎng)期時(shí)效的溫度越高,γ’相的粗化越明顯。長(zhǎng)期時(shí)效過(guò)程中,一般合金的顯微硬度會(huì)隨著時(shí)間的延長(zhǎng)而下降。γ’相長(zhǎng)期時(shí)效前后尺寸的立方差和時(shí)間成正比,1050℃的粗化系數(shù)要高于900℃γ’相粗化系數(shù),說(shuō)明1050℃長(zhǎng)期時(shí)效過(guò)程中γ’相粗化速度要高于900℃。在冷熱疲勞的實(shí)驗(yàn)中發(fā)現(xiàn):DD5合金第二取向?yàn)閇110]和[100]的裂紋擴(kuò)展方向都是與枝晶生長(zhǎng)方向成45°;但是第二取向[110]樣品在裂紋擴(kuò)展程度上要比第二取向[100]樣品明顯要多。單晶高溫合金的內(nèi)部缺陷組織,孔周?chē)难趸瘜佣紝?duì)裂紋擴(kuò)展有巨大的影響。
[Abstract]:With the continuous development of domestic aero-engine industry, nickel base single crystal superalloy is in a high speed development stage, the preparation process of single crystal has been quite mature. Therefore, it is more valuable to study the microstructure and properties of single crystal alloys during heat treatment and service, which is of great significance to improve the properties of the alloys and to understand the high temperature stability and life prediction of the alloys. In addition, with the application of film cooling technology to domestic single crystal blades, the temperature bearing capacity of domestic turbine engines has been further increased, but the mechanism of crack initiation and propagation around the gas film holes under thermal fatigue cycle has not been studied and explored. In this paper, the microstructure and properties of the second generation Ni-base single crystal superalloy DD5 are studied during heat treatment, and the microstructure evolves during the service at high temperature. And the crack initiation and propagation around the circular hole under the cold and thermal fatigue cycle of the alloy. In this paper, the temperature range of solution treatment for DD5 single crystal superalloy is determined by JMatPro and DSC curves. The results of solution treatment and aging treatment showed that both homogenization treatment and high temperature solution treatment could improve the dendritic segregation in the alloy structure, and the cooling mode after solution treatment could affect the morphology of 緯 'structure. The water cooling is 緯 'structure with the size below 100nm precipitated, the structure of the furnace is very large after cooling, and the size exceeds 600 nm. The 緯' particles after air cooling are arranged in a uniform and orderly manner. The microhardness of the air-cooled alloy after solid solution treatment is about 465, which is 120 higher than that of the as-cast structure, while the microhardness of the water-cooled sample treated by solid solution treatment is the highest. Aging treatment in heat treatment further adjusts the size and morphology of 緯'in the alloy. It is found that when the temperature of primary aging (high temperature aging) is too low, round 緯 'particles will appear, showing irregular arrangement. When the temperature increases, the 緯 'particles are arranged in cubic order gradually, thus the ordered cubic 緯' phase is obtained, and when the temperature continues to rise, the edge angle of the standard cubic 緯 'phase particle is passivated. In this paper, the optimum heat treatment process of DD5 single crystal superalloy is obtained as follows: 1: 1270 鈩，

本文編號(hào)：2146429