Mapula Matjee

Stress Corrosion Cracking resistance to grade 2205 Duplex Stainless Steel weldments
Refueling water storage tanks (PTR) made from Austenitic Stainless Steel material at Koeberg Nuclear Power Station experienced defects that manifested themselves in a form of boron crystals.  It was imperative that these tanks need be replaced with a more robust material; in this case Duplex Stainless Steel (DSS) grade 2205 was used.

During fabrication of the tanks, extensive welding on the formed plate material and significant weld repairs exposed the DSS weldments to the additional thermal cycles that could have affected the properties of the heat affected zones negatively. There was no post weld heat treatment applied to the welds and their Stress Corrosion Cracking (SCC) resistance in “as welded” condition needs to be established. Non Destructive Test (NDT) does not seem to be a viable technique to reveal the SCC defects for short and long term SCC testing.

My research will focus on the following:

  • Development of short term SCC test to characterise the SCC resistance on the representative welded plates
  • Confirming the SCC resistance on the sample of the welded plate for the new fabricated tank
  • Development of a short term and a long term testing technique for SCC for “As Weld” conditions