| Budget Amount *help |
¥8,500,000 (Direct Cost: ¥8,500,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1988: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1987: ¥7,300,000 (Direct Cost: ¥7,300,000)
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| Research Abstract |
A. The purpose of the present study
The purpose of the present study is to examine the orientation dependence of yield, creep and fatigue strengths of single crystals of Ni-base superalloys with different chemical compositions, and to show the alloy with excellent properties for practical use.
B. Procedures and results of the present study
1) Materials: Three kinds of Ni-base superalloys, 1) Al-Ti-Ta type, 2) Al-Ti-V type, 3) Al-Si type.
2) Tensile tests: Single crystals of the three kinds of alloys were subjected to tensile tests at room temperature up to 1000ﾟC. Orientation dependences of proof stress and CRSS were examined. Around 700ﾟC, the [001] orientation had the highest strength in three kinds of alloys. At 900ﾟC and 1000ﾟC, the alloys 2 and 3 had the highest strength in the [001], while the alloy 1 exhibited the highest strength in the [115] and [014] orientations.
3) Creep strength: The alloys 1 and 2 were subjected to creep tests. Typical five orientations with low indices were s
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elected as the initial tensile orientations. Testing temperatures were 700ﾟC and 9000ﾟC. At 7000ﾟC, the [001] exhibited the longest rupture times compared with those of the other orientations in both the alloys 1 and 2. At 9000ﾟC, however, the [113] or [111] showed longer rupture times than the [001]. The alloy 1 had longer rupture times compared with the alloy 2, if compared in the same testing conditions.
4) High temperature fatigue: The high cycle fatigue tests were performed at 7000ﾟC using the alloy 1 with the orientations of [001], [011] and [111]. The form of applied stress was a perfectly antisymmetric triangular form in tension.
The frequency was 5Hz. The S-N curves of the three orientations were resembled each other. Thus, it was found that the orientation dependence of fatigue strength is small.
C. Conclusions: According to the previous studies, it has been reported that the [001] orientation is the strongest orientation. In the present study, however, the different results have been obtained, i.e. the orientation dependence of yield strength, that of creep strength and that of fatigue strength were different each other. In both the yield strength and creep strength, the alloy 1 exhibited higher strengths compared with the alloy 2 in the same testing condition. Less
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