合金元素对Co-8.8Al-9.8W合金强化相粗化行为的影响

发布时间：2018-08-06 17:09

【摘要】：随着航空航天事业的发展,对于航天发动机性能的要求也越来越高,而发动机的好坏依靠制造发动机的高温合金的综合性能。一直以来,通过γ/γ′两相组织共格强化的镍基高温合金应用最为广泛,但是其承温能力的限制,制约了合金的发展。2006年发现在Co-Al-W合金中存在与镍基高温合金相似的γ/γ′两相组织,这与传统钴基高温合金主要通过碳化物弥散强化和合金元素固溶强化的方式不同,因此该合金受到国内外学者的广泛关注。通过研究合金元素对Co-8.8Al-9.8W合金强化相高温粗化行为的影响,得出的主要研究结果如下:在1000℃下对不同Ni含量Co-8.8Al-9.8W合金高温短时热处理时发现,5Ni,10Ni合金在经10h热处理时γ′相基本溶解;25Ni和35Ni合金随着时效时间的延长,γ′相不断长大,其形貌从立方状渐变到不规则形状,最终趋于圆球状,而且γ′相体积分数逐渐减小;25Ni和35Ni合金在经25h热处理时γ′相体积分数下降显著,继续延长时效处理时间,合金中γ′相体积分数会持续降低至某一平衡值或完全溶解消失;γ′相粗化行为符合LSW粗化理论,25Ni和35Ni合金粗化速率分别为4.05667×10-25m3s-1和2.78492×10-25m3s-1,25Ni合金中γ′强化相随时间粗化更快。时效处理过程中,随着时效时间的延长合金显微硬度值降低,15Ni合金硬度显著高于其他三种合金;1000℃/5h~25h,15Ni、25Ni和35Ni合金硬度变化趋于平缓,下降幅度较小;而5Ni合金硬度下降程度显著。硬度值大小顺序:15Ni25Ni35Ni5Ni。其中温度对合金硬度的影响更加显著。不同合金元素Co-8.8Al-9.8W基高温合金经870℃,900℃和930℃时效处理(50h,100h,200h,300h)后,5种合金随时效温度和时间的增加,γ′相尺寸增加,数量明显减少。2Ta,2Nb和2Ti合金中γ′相均保持较高的立方度,γ′相边缘未观察到球化现象;而2Mo和2Ni合金中γ′相为立方状或近立方状,γ′相边缘出现球化,并且γ基体通道明显变宽;2Mo合金在870℃和900℃处理时粗化速率K最大,3种温度下2Ni合金粗化速率K值均最小。2Ti合金K值明显低于2Ta和2Nb合金,粗化速度较慢,但是合金初始γ′相尺寸在5种合金中最大。不同温度下,从870℃升高到900℃,5种合金粗化速率K呈现减少趋势,而温度升高到930℃,粗化速率比870℃要高许多。合金在870、900和930℃下长期时效下γ′相尺寸满足LSW粗化理论。在870℃、900℃和930℃下合金微观组织中发现,合金中不同程度的出现了二次有害相。随着时效时间的延长,各种合金中二次相不断增加。870℃下300h,除了2Ni合金以外其他四种合金的微观组织中发现二次析出相。2Mo合金在晶界处出现大量块状和针状D019(Co3W)相,长针状D019相向着晶内延伸。2Nb和2Ta合金与2Mo合金析出的二次相相同,但是2Ti合金在晶界交界处出现了块状的Co Al相。2Ni合金中没有发现二次相的存在。在二次相存在的区域附近发现Co元素含量高达80%以上,可能是因为二次相的形成消耗了附近的合金元素导致。
[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.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG132.3

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