發(fā)布時(shí)間：2018-06-09 04:50

  本文選題：低錸鎳基高溫合金 + 單晶渦輪葉片��； 參考：《江蘇大學(xué)》2017年碩士論文

【摘要】：作為航空發(fā)動(dòng)機(jī)中工作環(huán)境最惡劣、結(jié)構(gòu)最為復(fù)雜的熱端部件,航空渦輪葉片是發(fā)動(dòng)機(jī)中最核心的部件之一,隨著先進(jìn)航空發(fā)動(dòng)機(jī)的發(fā)展,渦輪葉片服役溫度和工作載荷不斷提升,先進(jìn)單晶渦輪葉片的制造技術(shù)已經(jīng)成為了航空工業(yè)的關(guān)鍵技術(shù)[1]。因而,研究新型高性能單晶渦輪葉片的制備、優(yōu)化工藝,探討其力學(xué)性能和失效機(jī)制具有重要的實(shí)用意義。本文主要針對一種低錸高性能鎳基單晶高溫合金,采用快速凝固法(HRS)制備單晶渦輪葉片,研究定向凝固參數(shù)對渦輪葉片組織的影響;另外還探討了熱處理工藝對合金微觀組織和力學(xué)性能的影響;最后測定了單晶試樣的室溫強(qiáng)度和高溫蠕變性能,分析其斷裂機(jī)理。研究結(jié)果如下:單晶渦輪葉片凝固規(guī)律研究表明:對于新型高溫合金和選定渦輪葉片結(jié)構(gòu),一次枝晶間距隨抽拉速度的加快和型殼保溫溫度升高而減小,并且當(dāng)抽拉速度為1mm/min和4mm/min時(shí)都會(huì)導(dǎo)致鑄件出現(xiàn)雜晶。制備的渦輪葉片各部位組織不均,葉片壁厚較厚處一次枝晶間距、共晶相面積相對壁厚較薄處更大。枝晶臂處強(qiáng)化相尺寸遠(yuǎn)大于枝晶軸處。熱力學(xué)模擬和實(shí)驗(yàn)研究表明:合適的熱處理不僅能夠消除低溫共晶相,還可以極大的改善鑄態(tài)合金不均勻的組織。工藝參數(shù)對熱處理效果的影響表現(xiàn)為:較低的固溶溫度無法完全消除共晶相和粗大的γ'相組織,較高的固溶溫度會(huì)使得組織微熔。合金中析出的γ'相尺寸隨時(shí)效溫度的升高逐漸增加,立方度先增加后減少;固溶時(shí)間和時(shí)效時(shí)間過長都會(huì)導(dǎo)致γ'相邊角圓鈍。對合金的室溫強(qiáng)度研究表明:枝晶組織的枝晶軸處的硬度最高,超過410HV,枝晶間的共晶組織顯微硬度遠(yuǎn)低于枝晶內(nèi)部,僅有約365HV;熱處理能夠消除這種性能差異并使合金最高硬度提升到450HV;熱處理后合金室溫抗拉強(qiáng)度能夠達(dá)到1030MPa。室溫下合金的斷裂方式為脆性斷裂。新型鎳基單晶合金的高溫蠕變性能研究表明:在1100℃/100MPa、1100℃/120MPa、1100℃/140MPa三種測試條件下壽命分別為450h、260h、100h左右。在此溫度下,合金的蠕變第一階段不明顯,迅速進(jìn)入第二階段。第二階段的持續(xù)時(shí)間隨應(yīng)力增加顯著縮短。其斷裂都是蠕變微孔聚集長大所引起的。在1100℃蠕變過程中合金組織發(fā)生了明顯的垂直應(yīng)力軸的形筏現(xiàn)象,隨應(yīng)力增加筏形組織不斷增厚,形筏方向在靠近斷口處產(chǎn)生小角度改變,斷口處的筏形已經(jīng)完全破碎。
[Abstract]:As one of the most difficult and complicated hot end parts in aero-engine, the aero-turbine blade is one of the core components in the engine. With the development of advanced aero-engine, With the increasing service temperature and working load of turbine blades, advanced manufacturing technology of single crystal turbine blades has become a key technology in aviation industry [1]. Therefore, it is of great practical significance to study the preparation, optimization process, mechanical properties and failure mechanism of new high performance single crystal turbine blades. In this paper, single crystal turbine blades were prepared by rapid solidification method for a high performance nickel base single crystal superalloy with low rhenium and high performance. The effect of directional solidification parameters on the microstructure of turbine blades was studied. In addition, the effect of heat treatment on the microstructure and mechanical properties of the alloy was discussed, and the room temperature strength and high temperature creep property of the single crystal sample were measured, and the fracture mechanism was analyzed. The results are as follows: the solidification law of single crystal turbine blade shows that for the new superalloy and selected turbine blade structure, the primary dendrite spacing decreases with the increase of the drawing speed and the heat preservation temperature of the shell. And when the drawing speed is 1mm/min and 4mm/min, the castings will appear heterocrystals. The structure of the turbine blade is uneven, and the primary dendrite spacing of the blade is thicker, and the area of eutectic phase is larger than that of the thin one. The size of the strengthened phase at the dendrite arm is much larger than that at the dendrite axis. The thermodynamic simulation and experimental study show that the suitable heat treatment can not only eliminate the eutectic phase at low temperature, but also greatly improve the inhomogeneous microstructure of the as-cast alloy. The effect of process parameters on heat treatment effect is as follows: lower solution temperature can not completely eliminate eutectic phase and coarse 緯 'phase structure, and higher solution temperature will make microstructure micromelt. The size of 緯 'phase in the alloy increases gradually with the increase of the effect temperature, and the cubic degree increases first and then decreases, and both the solution time and aging time lead to the obtuse of the edge angle of 緯' phase. The study on the room temperature strength of the alloy shows that the microhardness of the dendritic microstructure at the dendrite axis is the highest, which is more than 410 HV.The microhardness of the eutectic microstructure between the dendrites is much lower than that of the dendrite interior. Only about 365 HVT; heat treatment can eliminate this difference and increase the maximum hardness of the alloy to 450 HV.The tensile strength of the alloy at room temperature can reach 1030 MPA after heat treatment. The fracture mode of the alloy at room temperature is brittle fracture. The creep properties of the new Ni-base single crystal alloy at high temperature have been studied. The results show that the lifetime of the new Ni-base single crystal alloy is about 450 h / 260 h / 100 h at 1100 鈩，

本文編號(hào)：1999010