STRESS CORROSION CRACKING OF AISI TYPE 316L AND COLD WORKED AISI TYPE 304 STAINLESS STEEL IN HIGH TEMPERATURE PRESSURISED WATER

摘要

Stress Corrosion Cracking tests of AISI 316L and 304 Stainless Steel with different degree of cold work from 20% to 45% has been carried out at 290°C and 90 bar high purity (Conductivity < 0.1 μS.cm~(-1)) water with 200 ppb of dissolved oxygen. Water chemistry parameters were continually monitored both at the inlet and at the outlet of the autoclave. Especially designed High Temperature (HT) and pressure cell enabled measuring corrosion potential, HT conductivity and HT pH at similar conditions as the exposed specimens. Single Edge Bend SEN(B) 10 × 10 × 55 (mm) specimens were loaded by means of a Pneumatic Servo Controlled Fracture Mechanics (PSCFM) system. The autoclave system enabled installation of two PSCFM systems at the same time. Rising Displacement Tests (RDT) with different displacement rates and Constant Load (CL) tests were carried out. Displacement rates were also changed during the tests several times. Crack Growth was monitored in-situ by Direct Current Potential Drop (DCPD). Fracture surface analysis was carried out by SEM and crack growth rates were precisely calculated. Elastic- Plastic Fracture Mechanics (EPFM) parameter J-integral was used for the evaluation of the stress.