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

1996 Fiscal Year Final Research Report Summary

• Project/Area Number: 07555532
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 試験
• Research Field: Material processing/treatments
• Research Institution: Ritsumeikan University
• Principal Investigator: AMEYAMA Kei Ritsumeikan University, Department of Mechanical engineering, Prof., 理工学部, 教授 (10184243)
• Co-Investigator(Kenkyū-buntansha): ISONISHI Kazuo Shiga University, Associate Professor, 教育学部, 助教授 (50223061) ; KUMAGAE Ryohei Fukuda Powder & Foil Co.
• Project Period (FY): 1995 – 1996
• Keywords: Intermetallic compound / Niobium aluminido / Nb / Al / mechanical alloying / PREP / Pseudo-HIP / SHS

Research Abstract

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.