Stress corrosion cracking of alloy C-22 and Ti Gr-12 using double-cantilever-beam technique

Susceptibility to stress corrosion cracking (SCC) of two candidate alloys f or the inner container of the multi-barrier nuclear waste package was evalu ated by using wedge-loaded precracked double-cantilever-beam (DCB) specimen s in deaerated acidic brine (pH approximate to 2.70) at 90 degrees C. Mater ials tested included Alloy C-22 and Ti Grade-12. Duplicate samples of each material were loaded at different initial stress intensity factor (K-I) val ues ranging between 22 and 43 MPa root m. Both metallography and the compli ance methods were used to determine the final crack length. The final stres s intensity for SCC (Kf) was computed from the measured final wedge load an d the average crack length. The results indicate that, in general, the fina l crack lengths measured by metallography and compliance agreed well with o ne another, thus, providing very similar K-f values. The alloy C-22 showed higher susceptibility to SCC than Ti Grade-12 in terms of the average crack growth. Fractographic evaluation by scanning electron microscopy (SEM) of broken DCB, specimens revealed three distinct regions showing the character istics of fatigue precrack, SCC, and fast fracture. (C) 1999 Elsevier Scien ce Ltd. All rights reserved.