<研究報告>ニッケル基単結晶合金の組織と相安定性 : ニッケル基単結晶超耐熱合金の研究(第1報)

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Ni-base single crystal superalloys have benn developed for improving the performance of jet engines. Their alloy properties are very sensitive to the microstructure. The occurrence of topologically-close-packed (TCP) phases in the γ matrix deteriorate significantly mechanical properties of alloys. In this study, both the microstructure and the phase stability were investigated with the single crystal superalloys, Ni-11at%Cr-14at%Al-W-Ta and Ni-11at%Cr-14at%Al-Co-W-Ta. Sixty specimens were totaly prepared, changing the Co, W and Ta contents. After aging at 900℃ for 500hr, TCP phases were observed in those alloys which have higher W and Ta contents. With increasing Co content, the γ+γ'/γ+γ'+TCP phase boundary (γ' : Ni_3Al) shifts to the lower Ta and the lower W side and shows a curvature toward the origin of the Ta-W diagram. For the compositional analysis, the γ' was extracted using 1% sulphate ammonium-1% tartaric acid solution. The muximum γ' volume fraction is about 67 vol% in the case of the non-existence of eutectic phase. Co, Cr and W prefer to partition into the γ, while Al and Ta partition mostly into the γ'. For comparison, similar experiment was carried out by using NASAIR-100 and PWA-1480 that are well-known single crystal superalloys.
沼津工業高等専門学校の論文
1986-01-31