【摘要】：隨著航空航天事業(yè)的發(fā)展,對于航天發(fā)動(dòng)機(jī)性能的要求也越來越高,而發(fā)動(dòng)機(jī)的好壞依靠制造發(fā)動(dòng)機(jī)的高溫合金的綜合性能。一直以來,通過γ/γ′兩相組織共格強(qiáng)化的鎳基高溫合金應(yīng)用最為廣泛,但是其承溫能力的限制,制約了合金的發(fā)展。2006年發(fā)現(xiàn)在Co-Al-W合金中存在與鎳基高溫合金相似的γ/γ′兩相組織,這與傳統(tǒng)鈷基高溫合金主要通過碳化物彌散強(qiáng)化和合金元素固溶強(qiáng)化的方式不同,因此該合金受到國內(nèi)外學(xué)者的廣泛關(guān)注。通過研究合金元素對Co-8.8Al-9.8W合金強(qiáng)化相高溫粗化行為的影響,得出的主要研究結(jié)果如下:在1000℃下對不同Ni含量Co-8.8Al-9.8W合金高溫短時(shí)熱處理時(shí)發(fā)現(xiàn),5Ni,10Ni合金在經(jīng)10h熱處理時(shí)γ′相基本溶解;25Ni和35Ni合金隨著時(shí)效時(shí)間的延長,γ′相不斷長大,其形貌從立方狀漸變到不規(guī)則形狀,最終趨于圓球狀,而且γ′相體積分?jǐn)?shù)逐漸減小;25Ni和35Ni合金在經(jīng)25h熱處理時(shí)γ′相體積分?jǐn)?shù)下降顯著,繼續(xù)延長時(shí)效處理時(shí)間,合金中γ′相體積分?jǐn)?shù)會(huì)持續(xù)降低至某一平衡值或完全溶解消失;γ′相粗化行為符合LSW粗化理論,25Ni和35Ni合金粗化速率分別為4.05667×10-25m3s-1和2.78492×10-25m3s-1,25Ni合金中γ′強(qiáng)化相隨時(shí)間粗化更快。時(shí)效處理過程中,隨著時(shí)效時(shí)間的延長合金顯微硬度值降低,15Ni合金硬度顯著高于其他三種合金;1000℃/5h~25h,15Ni、25Ni和35Ni合金硬度變化趨于平緩,下降幅度較小;而5Ni合金硬度下降程度顯著。硬度值大小順序:15Ni25Ni35Ni5Ni。其中溫度對合金硬度的影響更加顯著。不同合金元素Co-8.8Al-9.8W基高溫合金經(jīng)870℃,900℃和930℃時(shí)效處理(50h,100h,200h,300h)后,5種合金隨時(shí)效溫度和時(shí)間的增加,γ′相尺寸增加,數(shù)量明顯減少。2Ta,2Nb和2Ti合金中γ′相均保持較高的立方度,γ′相邊緣未觀察到球化現(xiàn)象;而2Mo和2Ni合金中γ′相為立方狀或近立方狀,γ′相邊緣出現(xiàn)球化,并且γ基體通道明顯變寬;2Mo合金在870℃和900℃處理時(shí)粗化速率K最大,3種溫度下2Ni合金粗化速率K值均最小。2Ti合金K值明顯低于2Ta和2Nb合金,粗化速度較慢,但是合金初始γ′相尺寸在5種合金中最大。不同溫度下,從870℃升高到900℃,5種合金粗化速率K呈現(xiàn)減少趨勢,而溫度升高到930℃,粗化速率比870℃要高許多。合金在870、900和930℃下長期時(shí)效下γ′相尺寸滿足LSW粗化理論。在870℃、900℃和930℃下合金微觀組織中發(fā)現(xiàn),合金中不同程度的出現(xiàn)了二次有害相。隨著時(shí)效時(shí)間的延長,各種合金中二次相不斷增加。870℃下300h,除了2Ni合金以外其他四種合金的微觀組織中發(fā)現(xiàn)二次析出相。2Mo合金在晶界處出現(xiàn)大量塊狀和針狀D019(Co3W)相,長針狀D019相向著晶內(nèi)延伸。2Nb和2Ta合金與2Mo合金析出的二次相相同,但是2Ti合金在晶界交界處出現(xiàn)了塊狀的Co Al相。2Ni合金中沒有發(fā)現(xiàn)二次相的存在。在二次相存在的區(qū)域附近發(fā)現(xiàn)Co元素含量高達(dá)80%以上,可能是因?yàn)槎蜗嗟男纬上牧烁浇暮辖鹪貙?dǎo)致。
[Abstract]:With the development of Aeronautics and Astronautics, the requirements for the performance of the space engine are becoming higher and higher, and the good or bad of the engine depends on the comprehensive performance of the superalloy which makes the engine. The application of the nickel base superalloy with the co enhancement of gamma / gamma phase structure has been the most widely used, but the limitation of its temperature bearing capacity restricts the alloy. In the development of.2006, it was found that there were gamma / gamma two phase structures similar to nickel base superalloys in Co-Al-W alloys. This is different from the traditional cobalt base superalloy by means of dispersion strengthening of carbide and solid solution strengthening of alloy elements. Therefore, the alloy has been widely used by scholars both at home and abroad. By studying the alloy elements to the Co-8.8Al-9.8W alloy, the alloy has been studied. The main results are as follows: at high temperature and short time heat treatment of Co-8.8Al-9.8W alloy with different Ni content at 1000 C, it is found that 5Ni, 10Ni alloys are basically dissolved in the 10h heat treatment, and 25Ni and 35Ni alloys grow with the prolongation of aging time, and their morphology is from cubic The volume fraction of gamma phase decreases gradually and the volume fraction of gamma phase decreases significantly in 25Ni and 35Ni alloys during 25h heat treatment. The volume fraction of gamma phase in the alloy will continue to decrease to a certain equilibrium value or completely dissolve, and the roughening behavior of gamma phase conforms to L. SW coarsening theory, the coarsening rate of 25Ni and 35Ni alloy is 4.05667 x 10-25m3s-1 and 2.78492 x 10-25m3s-1,25Ni alloy respectively. The hardening phase is quicker with time. In the aging treatment, the microhardness of the alloy decreases with the prolongation of aging time, and the hardness of 15Ni alloy is significantly higher than that of the other three alloys; 1000 C /5h~25h, 15Ni, 25Ni and 35Ni. The hardness of the alloy tends to be slow and the decrease is smaller, while the hardness of 5Ni alloy decreases significantly. The order of hardness value is 15Ni25Ni35Ni5Ni., and the effect of temperature on the hardness of the alloy is more significant. The 5 alloys of different alloy elements Co-8.8Al-9.8W base superalloys are treated at 870, 900, and 930 C (50h, 100h, 200H, 300h) at any time. With the increase of effective temperature and time, the size of gamma phase increases and the number of.2Ta decreases obviously. The gamma phase in 2Nb and 2Ti alloys keeps a high cubic degree. The spheroidizing phenomenon is not observed on the edge of the gamma phase, while the gamma phase in 2Mo and 2Ni alloys is cubic or near cubic, the edge of the gamma phase appears spheroidizing, and the gamma matrix channel is broadened obviously; 2Mo alloy is 870 The coarsening rate of K is the largest at temperature and 900 C, and the K value of 2Ni alloy coarsening at 3 temperatures is the smallest.2Ti alloy K value is obviously lower than 2Ta and 2Nb alloy, and the coarsening speed is slower, but the initial size of the alloy is the largest in the 5 alloys. At different temperatures, from 870 to 900, the 5 kind of alloy coarsening rate K presents a decreasing trend, and the temperature rises. At 930 C, the coarsening rate is much higher than that at 870. The size of the alloy at 870900 and 930 centigrade is satisfied with the LSW coarsening theory. At 870, 900 and 930, the alloy is found to have two harmful phases in the alloy at different degrees. As the aging time prolongs, the two phases of the alloys increase by.870 continuously. At 300h, the microstructures of the four alloys other than the 2Ni alloy were found in the microstructures of the four alloys other than the 2Ni alloy. A large number of massive and needle like D019 (Co3W) phases appeared at the grain boundary, and the long acicular D019 was extended to the intragranular.2Nb and the 2Ta alloy was the same as the two phase precipitated from the 2Mo alloy, but the 2Ti alloy appeared in the bulk of Co Al phase at the boundary between the grain boundary. The existence of the two phase was not found in the 2Ni alloy. The content of the Co element was found to be over 80% near the region of the two phase, probably because the formation of the two phase was caused by the alloying elements in the vicinity.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG132.3

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