Abstract
The fracture toughness (J1c) of modified 9Cr-1Mo (P91 or Grade 91) steel was evaluated in the temperature range 300-550 °C. The yield strength and ultimate tensile strength values were observed to decrease with test temperatures. The ductility (% uniform elongation and post-necking elongation) was minimum in the temperature range 350-400 °C. From J–R curves established at 300, 350, 400, 450, 500, and 550 °C, fracture toughness (J1c) and tearing modulus were determined at different loading rates of 0.01, 0.05 and 0.1 mm/s. For all the loading rates, J1c values decreased in the temperature range 300-450 °C, followed by an increase in fracture toughness up to 550 °C. These trends in tensile and fracture properties can be attributed to the influence of dynamic strain aging.
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