STRESS CORROSION CRACKING OF ALLOY 152 WELD BUTTER NEAR THE LOW ALLOY STEEL INTERFACE

Conference · Thu Jan 01 04:00:00 EST 2015

OSTI ID:1351993

Alexandreanu, Bogdan; Chen, Yiren; Natesan, Ken; Shack, William J.

The objective of this work was to obtain SCC growth data in Alloy 152 weld butter near the interface with Low Alloy Steel (LAS), which is a region where some dilution of Cr was expected to have occurred, thus presumably exhibiting an increased SCC-susceptibility vs. the bulk of the weld. The LAS piece used in this application was Alloy 533-Gr B from the Midland reactor lower head, and the Alloy 152 weld butter received a prototypical Post Weld Heat Treatment (PWHT) prior to joining by Alloy 152 to an Alloy 690 piece according to a procedure qualified to ASME IX. The compact tension specimens for SCC testing were aligned in the first layer of the Alloy 152 butter. The experimental approach based on tracking environmental enhancement vs. location was successful in identifying SCC-susceptible locations, and SCC rates ranging from 10-12 m/s to as high as 10-10 m/s were measured. The post-test examination of the specimens found that the fracture had the intergranular/interdendritic appearance typical of welds, and that the propagation was arrested wherever an intersection with the LAS occurred. The large range of SCC rates measured does not appear to correlate well with the local concentration of Cr (approx. 25% at the SCC locations), and, in fact, low Cr (20%) – high Fe “streaks” seemed to slow/arrest crack propagation. In short, simple “Cr dilution” does not seem to fully account for the “SCC-susceptible” microstructure that yielded the 10-10 m/s growth rate in this weld.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: U. S. Nuclear Regulatory Commission (NRC)
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1351993
• Country of Publication: United States
• Language: English

Related Subjects

Alloy 152
Cr dilution
Stress Corrosion Cracking