Determination of crack growth rate and threshold for caustic cracking (KISCC) of a cast iron using small circumferential notched tensile (CNT) specimens

A novel fracture mechanics technique has been employed for the determination of crack growth rate and threshold stress intensity factor (K-Iscc) for stress corrosion cracking (SCC) using small circumferential notch tensile (CNT) specimens. The technique was applied successfully for testing SCC susceptibility of spheroidal graphite (SG) cast iron in 5 M NaOH at 100 and 120 degrees C. Crack growth rate of SG cast iron in 5 M NaOH solution at 100 and 120 degrees C has been determined at different stress intensity factors (K-I), and the K-Iscc have been determined to be 11.2 and 9 MPa m(1/2), respectively. The surfaces of fractured specimens have been examined by scanning electron microscopy (SEM) in order to establish intergranular propagation of stress corrosion cracks. CNT testing is a simple, relatively fast and cost-advantageous approach for generating crack growth rate and K-Iscc data. (c) 2006 Elsevier B.V. All rights reserved.