<研究報告>Ni-12at%Al-10at%Cr-0/2at%Ti-Ta-W系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2報)

概要

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In developing Ni-base single-crystal superalloys, overall study involving microstructure, phase stability, mechanical properties, hot corrosion resistance etc. is important. In this study, to improve hot corrosion resistance of high W content alloys, Ti-containing systems, Ni-12at%Al-10at%Cr-0/2at%Ti-Ta-W, were selected and their microstructure and phase stability were investigated systematically. For comparison, NASAIR-100 that is a well-known single crystal superalloy was also studied. The eutectic γ' phase was observed in high Ta content alloys, but its volume fraction decreased with increasing W content. The limit of the occurrence of the eutectic γ' phase was represented by a line drawn in the Ta vs. W concentration diagram. The TCP phase was observed in the alloys aged at 900℃ for 500hr. But with decreasing alloy concentration of Ta and W, it scarcely occurred in the matrix. The γ+γ'/ γ+γ' +TCP phase boundary was estimated well by the γ phase composition calculated by a multiple regression analysis. The a-W phase was observed mainly in high W content alloys. The critical composition of the occurrence of this phase was found to be 4〜5at%W for Oat%Ti alloys and 3〜4at%W for 2at%Ti alloys. By the Ti addition, these three boundaries shifted to the lower concentration side in the Ta vs. W concentration diagram.
沼津工業高等専門学校の論文
1987-01-31