Production and Microstructure Control of High Strength Nb Base Superalloy by PM Processing

目前的燃气轮机和航空发动机涡轮技术以及航空发动机涡轮在高温区域的建筑材料中严重依赖镍基高温合金。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，本研究的重点是利用粉末冶金技术开发一种具有发展潜力的新型铌基高温合金。采用机械合金化（MA）工艺和等离子体旋转电极（FREP）工艺。结果如下：(1)研究了添加碳对Nb-Al MA加工的影响。Nb_2C分布在Nb固溶体和Nb_3A1金属间化合物中，有利于强化。(2)研究了硅含量对铌硅MA加工的影响。Si含量越大，非晶态形成的倾向越大。形成Nb_5Si_3金属间化合物，有利于强化。(3)采用伪HIP-SHS工艺制备Nb-Al PREP电极。用该方法成功制备了NB-Al PREP粉末。

The current technology for both gas turbines and aero engine turbines and aero engine turbines relies heavily on the nickel-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, the 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 a new potential Nb based superalloy by Powder Metallurgy (PM) processing. The PM process we applied is Mechanical Alloying (MA) process and Plasma Rotating Electrode Process (FREP). The results are as follows.(1) Effect of carbon addition on Nb-Al MA processing is investigated. Nb_2C is distributed in Nb solid solution and Nb_3A1 intermetallic compound and contributed to the strengthening.(2) Effect of Si content on Nb-Si MA processing is investigated. Larger amount of Si lead to higher tendency of the amorphous formation. Nb_5Si_3 intermetallic compound is formed and contributed to the strengthening.(3) Pseudo HIP-SHS process is applied to produce Nb-Al PREP electrode. NB-Al PREP powder was successfully produced by this process.