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

摘要

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 at elevated temperature was characterized using both fracture mechanics and Charpy specimens. Aging at 566 sup 0 C for 10,000 hours reduced static j/sub c/ 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, as reported in this and other studies, was not representative of the impact resistance for SS components containing cracks or crack-like 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. 25 refs., 17 figs., 2 tabs. (ERA citation 12:047819)