SYMPOSIA PAPER Published: 01 January 1989

Effect of Loading Rate and Thermal Aging on the Fracture Toughness of Stainless-Steel Alloys


The effect of loading rate on the fracture toughness of Types 304 and 316 stainless-steel plate and Type 308 weld before and after thermal aging was characterized using both fracture mechanics and Charpy specimens. Aging at 566°C for 10 000 h reduced static Jc initiation toughness values for both wrought and weld metals by 10 to 20%, and tearing moduli were reduced by 20 to 30%. Under semi-dynamic and dynamic loading conditions, the fracture resistance was not decreased below the static response for either unaged or aged materials. The present results also demonstrated that the large degradation in Charpy V-notch impact energy after aging was not representative of the impact resistance for stainless-steel components containing cracks or crack-life defects. Fractographic examinations revealed that the large loss in Charpy energy was associated with aging-induced microstructural changes that substantially decreased the energy required to initiate a crack from a blunt notch. At very slow strain rates, creep crack growth was found to cause a significant degradation in fracture toughness.

Author Information

Mills, WJ
Westinghouse Electric Corporation, West Mifflin, PA
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Developed by Committee: E08
Pages: 459–475
DOI: 10.1520/STP18838S
ISBN-EB: 978-0-8031-5081-2
ISBN-13: 978-0-8031-1250-6