Investigation on Fracture Behavior of Grade 91 Steel at 300-550 degrees C

摘要

The fracture toughness (J(1c)) of modified 9Cr-1Mo (P91 or Grade 91) steel was evaluated in the temperature range 300-550 degrees 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 degrees C. From J-R curves established at 300, 350, 400, 450, 500, and 550 degrees C, fracture toughness (J(1c)) and tearing modulus were determined at different loading rates of 0.01, 0.05 and 0.1 mm/s. For all the loading rates, J(1c) values decreased in the temperature range 300-450 degrees C, followed by an increase in fracture toughness up to 550 degrees C. These trends in tensile and fracture properties can be attributed to the influence of dynamic strain aging.