Hydrogen embrittlement behavior of cast super duplex stainless steel and cast maraging steel was examined as a function of electrode potential and hydrostatic pressure, i.e, the water depth, in synthetic sea water using fracture mechanics bolt-loaded wedge-opening (WOL) specimens. The experimental variables investigated included: (1) Electrode potential: free corrosion potential and cathodic protection; (2) Hydrostatic pressure: ambient and 10 MPa corresponding depth of 1,000 meters. The duplex stainless-,steel was not susceptible to hydrogen embrittlement with initial stress intensity values of 30 MPa{radical}m < K{sub i} < 45 MPa{radical}m at ambient pressure. However, at pressure of 10 MPa slight crack growth was observed at open circuit potential and the crack growth was enhanced by the cathodic protection. The maraging steel was susceptible to hydrogen embrittlement in all tests, with all examined initial stress intensity values, K{sub i} < 36 MPa{radical}m. At the open circuit potential the crack growth rate was almost independent of the pressure. Cathodic protection enhanced crack growth and lowered the threshold stress intensity value at ambient as well as at 10 MPa pressure and the crack growth rate increased clearly as pressure increased from 0.1 MPa to 10 MPa. According to these experimental results the combined effect ofmore » cathodic protection and hydrostatic pressure must be taken into consideration when designing new offshore structures and equipment especially for deep sea application.« less
