Ni基超合金Inconel718の固相線温度近傍における力学特性取得に関する検討

摘要

Ni基超合金は高温強度，耐食性に優れていることから航空機エンジン部品やガスタービン動翼等の高温・高圧環境下にて用いられている．しかし，精密鋳造時において鋳造欠陥の一種である凝固割れが生じることがある．これらの製品は主に一方向凝固により製造されるが，一方向凝固においては製造に時間がかかり，用いるセラミック製の中子や鋳型が高価である．%Nickel-based superalloys have been applied to gas turbine and aircraft jet engine parts due to superior high temperature strength and corrosion resistance. However, casting defect such as solidification cracking often occurs. In order to increase productivity of precision casting and various shape casting processes, predicting the occurrence of solidification cracking by using CAE (Computer Aided Engineering) should be essential. Therefore, it is necessary to obtain mechanical properties in the state of solid-liquid coexistence. In this study, we try to get high temperature (around solidus temperature) mechanical properties of the nickel-based superalloy such as Inconel 718 by using originally developed tensile test. In the previous reports, flat distribution of temperature in the gage length, and crack initiation strain were not ensured. On the other, the developed device ensured within 3℃ of the temperature distribution in the gage length as to the Inconel 718. Tensile strain was measured by using in-situ observation of marker on the surface of the specimen. As a result, Stress-Strain curve, crack initiation stress, and crack initiation strain of Inconel 718 were obtained.