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Effect of temperature on the fracture toughness behavior of Inconel X-750

Conference ·
OSTI ID:5880536
The elastic-plastic J/sub Ic/ fracture toughness response of precipitation heat treated Inconel X-750 was evaluated by the multi-specimen resistance curve (R-curve) technique at room temperature and elevated temperatures. The fracture toughness of this nickel-base superalloy was found to increase slightly at intermediate temperatures (approximately 427/sup 0/C), but it decreased dramatically at the highest test temperature (649/sup 0/C). Metallographic and electron fractographic examination of the Inconel X-750 fracture surfaces revealed that the slight increase in J/sub Ic/ at intermediate temperatures was associated with an intergranular to transgranular fracture mechanism transition. Under room temperature conditions, crack extension occurred primarily by an intergranular dimple rupture mechanism attributed to microvoid coalescence along a grain boundary denuded region. In the 427 to 538/sup 0/C regime, the fracture surface was dominated by a transgranular morphology consisting of poorly defined dimples coupled with a rather flat, faceted appearance. At the highest test temperature (649/sup 0/C), intense heterogeneous slip initiated localized separation which resulted in a very faceted fracture surface morphology and a severe degradation in fracture toughness.
Research Organization:
Hanford Engineering Development Lab., Richland, WA (USA)
DOE Contract Number:
EY-76-C-14-2170
OSTI ID:
5880536
Report Number(s):
HEDL-SA-1818; CONF-791115-2
Country of Publication:
United States
Language:
English