THERMAL FATIGUE OF INCONEL ALLOY DA718
[Technical Report, Technical Memo]
NAVAL AIR WARFARE CENTER AIRCRAFT DIVISION
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UFOUOThe thermal fatigue behavior of an Inconel alloy DA718 was studied to clarify the induced axial stress, diametral strain, and change in microstructure and fractograph under thermal fatigue cycling between the predetermined maximum and minimum temperatures in air. The minimum axial stress became less compressive with increasing number of thermal fatigue cycle and temperature. The diametral strain was constant in the initial stage of thermal fatigue cycling but decreased later. The decrease occurred earlier at higher temperatures and during longer holding time. The intragrain precipitates gamma and gamma were grown, and gamma particle-depleted zones were formed near grain boundaries due to gamma to delta phase transformation during the thermal fatigue cycling. This microstructure change resulted in the variation of axial stress and diametral strain, intergranular cracking, and eventual thermal fatigue failure.
- Metallurgy and Metallography