An electronic approach to alloy design and its application to Ni-based single-crystal superalloys
✍ Scribed by K. Matsugi; Y. Murata; M. Morinaga; N. Yukawa
- Publisher
- Elsevier Science
- Year
- 1993
- Tongue
- English
- Weight
- 842 KB
- Volume
- 172
- Category
- Article
- ISSN
- 0921-5093
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✦ Synopsis
The d-electron concept was applied to the design of nickel-based single-crystal superalloys. This concept was devised on the basis of molecular orbital calculations for transition-metal-based alloys. Two calculated parameters were mainly utilized in this alloy design. One is the d-orbital energy level (Md) of alloying transition elements and the other is the bond order (Bo), which is a measure of the covalent bond strength between atoms. Using these parameters, accurate prediction is possible for the appearance of the 7 + 7' eutectic phase, the topologically close-packed phases and the a-W phase in the alloys. Also, the strengthening of both the y and y' phases in the alloys can be treated with these parameters. On the basis of this concept, single-crystal superalloys were designed successfully. Six kinds of designed alloys lay in the compositional range Ni-10mol.%Cr-12mol,%Al-1.5mol.%Ti-( 1.8-2.7)mol.%Ta-( 1.8-2.6)mol.%W-(0.6-0.9)mol.%Mo-0.25mol.%Re. It was confirmed experimentally that these designed alloys had excellent creep rupture properties, high hot corrosion resistance, low density and low material cost. In this respect the designed alloys are much superior to any single-crystal superalloys published in the literature to date.