Development of the manufacturing process of Nb-Al intermetallic compound by Pseudo-HIP/SHS processed PREP electrode

目前的燃气轮机和航空发动机涡轮技术严重依赖镍基高温合金作为高温区域的建筑材料。这些合金通常被限制在低于1150C的工作温度，尽管使用涂层和冷却系统允许涡轮入口温度高于镍本身的熔点（1453C）。尽管在发动机运行中使用更高的温度有一个普遍的优势，而且对这种系统的研究正在进行中，但这种对可靠性、成本和排放控制的要求对实际进展施加了一些相当严重的限制。在传统的吸气式发动机中，涡轮入口温度在理论上受到绝热化学燃烧温度的限制，根据所使用的燃料，在1800至2100C的范围内。然而，在实践中，由于控制氮氧化物排放的要求，即使是目前复杂的燃烧室设计也可能被限制在1650℃左右的进口温度。这一限制设定了高温区域内未冷却部件的使用温度目标。因此，本研究的重点是通过粉末冶金（PM）的新工艺来开发Nb-Al金属间化合物。我们采用的PM工艺是伪hip /SHS等离子体旋转电极工艺（PREP）结合或不结合机械合金化（MA）工艺。结果如下：(1) P-HIP/SHS法制备的电极微观结构粗大，主要由Nb固溶体（as）和Nb_2Al相组成。电极在1873K下退火36ks，组织均匀。机械合金化的P-HIP/SHS工艺表现出细小均匀的Nb ss+Nb_3Al显微组织。(2)三种电极制备的PREP粉体微观结构良好。采用伪hip /SHS等离子体旋转电极工艺成功制备了Nb-Al PREP粉末。

The current technology for both gas turbines and aero engine turbines relies haevily on the niclkel-base superalloys for construction materials in the high temperature regions. These alloys are generally limited to working temperatures below 1150C,although the use of coatings and cooling systems permits turbine inlet temperatures above the melting point of nickel itself (1453C). Although there is a general advantage in using higher temperatures in the engine operation, and the search for such systems is ongoing, ths requirements of reliability, cost and emission control impose some quite severe limits on practical progress. In conventional air-breathing engines the turbine inlet temperature is theoretically limited by the adiabatic stoichiometric combustion temperature, in the range of 1800 to 2100C depending on the fuel used. In practice, however, even the present sophisticated combustor designs are likely to be limited to an inlet temperature of around 1650C because of the requirement to control NOX emissions. This limit then sets the goal for the use-temperature of un-cooled components in the high temperature region.Therefore, this study is focused to develop Nb-Al intermetallic compounds by a novel Powder Metallurgy (PM) processing. The PM process we applied is Pseudo-HIP/SHS Plasma Rotating Electrode Process (PREP) combined with or without Mechanical Alloying (MA) process and. The results are as follows.(1) The electrode produced by a P-HIP/SHS process showed coarse microstructure consisted of Nb solid solution (as) and Nb_2Al phases. Annealing of the electrode at 1873K for 36ks resulted in homogeneous microstructure. The P-HIP/SHS process with a mechanical alloying proceeing showed very fine and homogeneous Nb ss+Nb_3Al microstructure.(2) The PREP powders made from above three kinds of electrode showed a fine microstructure. The Nb-Al PREP powders were successfully produced by the Pseudo-HIP/SHS Plasma Rotating Electrode Process.