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

目前用于燃气轮机和航空发动机涡轮的技术严重依赖于高温地区的镍基高温合金作为建筑材料。这些合金的工作温度一般限制在1150摄氏度以下，尽管涂层和冷却系统的使用允许涡轮机进口温度高于镍本身的熔点(1453摄氏度)。虽然在发动机运行中使用更高的温度具有普遍的优势，而且对这类系统的研究正在进行中，但可靠性、成本和排放控制的要求对实际进展施加了一些相当严格的限制。在传统的吸气式发动机中，理论上涡轮进口温度受绝热化学计量燃烧温度的限制，根据所用燃料的不同，该温度范围在1800到2100摄氏度之间。然而，在实践中，由于控制NOX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摄氏度左右的进口温度。这一极限为非冷却部件在高温区的使用温度设定了目标。因此，本研究的重点是通过一种新型的粉末冶金(PM)工艺来开发Nb-Al金属间化合物。我们采用的粉末冶金工艺是伪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)工艺和。结果表明：(1)采用P-HIP/SHS工艺制备的电极组织粗大，主要由Nb固溶体(As)和Nb_2Al相组成。电极在1873K下进行36K的热处理，得到了均匀的显微组织。采用机械合金化工艺制备的P-HIP/SHS电极具有非常细小、均匀的Nb、ss+Nb_3Al组织。(2)三种电极制备的PREP粉末均具有良好的组织结构。采用准等静压/自蔓延高温合成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.