What is it about?
This study compares thermal aging effects in Inconel 690 (IN690) produced by forging and powder metallurgy with hot isostatic pressing (PM-HIP). Isothermal aging is carried out over 400–800°C for up to 1000 h and then metallography and nanoindentation are utilized to relate grain microstructure with hardness and yield strength. The PM-HIP IN690 maintains a constant grain size through all aging conditions, while the forged IN690 exhibits limited grain growth at the highest aging temperature and longest aging time. The PM-HIP IN690 exhibits comparable mechanical integrity as the forged material throughout aging: hardness and yield strength are unchanged with 100 h aging, but increase after 1000 h aging at all temperatures. In both the PM-HIP and forged IN690, the Hall–Petch relationship for Ni-based superalloys predicts yield strength for 0–100 h aged specimens, but underestimates yield strength in the 1000 h aged specimens because of thermally induced precipitation.
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Why is it important?
Thermal aging effects IN690 for nuclear reactor applications.
Perspectives
Thermal aging generates precipitation after 1000h which strengthens the material beyond Hall-Petch relationship.
Dr. Keyou S. Mao
Purdue University
Read the Original
This page is a summary of: Comparative Thermal Aging Effects on PM-HIP and Forged Inconel 690, JOM, March 2018, Springer Science + Business Media,
DOI: 10.1007/s11837-018-2818-z.
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