Forged HP 9-4-20 steel exhibits a high yield strength (1240 MPa (180 ksi)), a high fracture toughness (K/sub Ic/) (120 MN/m/sup 3/2/ (110 ksi ..sqrt..in)), in good weldability. The alloy was studied to determine some of its corrosion and stress-corrosion characteristics, especially after welding. Potentiodynamic-polarization studies established that pitting of the steel was most severe when the chloride ion concentration was high and the pH of the solution was low. Higher potentials (approaching 1 V) caused increased corrosion rates also. Pitting of the welded samples was not preferential to any part of the weld and was uniform on both the base metal and weld. Dead-weight stress-corrosion tests demonstrated that welding did not increase susceptibility of the alloy to stress corrosion. The specimens failed in a ductile manner from the increased tensile load as the cross-sectional area was reduced by dissolution of the metal in the corrosive solution.
Date: February 20, 1979
Creator: Dobbins, A.G.; Koger, J.W. & Mustaleski, T.M. Jr.