Trends in the Electrochemical Polarization Potentiodynamic Reactivation Method – EPR

This method designed to examine the susceptibility to nonuniform corrosion, ranks among the more successful technique developments. One of its numerous advantages is that it allows nondestructive, on-site examination. EPR measurements are used to establish the resistance of stainless steels and alloys to intergranular corrosion and stress corrosion cracking e.g. in nuclear engineering applications as well as to study grain boundary precipitation and other minute local changes in alloy composition and structure. By the EPR test, the specimen and/or the field object (working electrode) is tested in acid solutions, most often in solutions of sulfuric acid (c = 0.01–5 mol dm–3 H2SO4) and potassium thiocyanate (c = 0.001 to 0.1 mol dm–3 KSCN). The principle of the measurements is to reactivate the sample from the incomplete passivity region. This indicates local changes in chemical composition in relation to phase transformations

Influence of gaseous hydrogen on metals

Tensile, fracture toughness, threshold stress intensity for sustained-load crack growth, and cyclic and sustained load crack growth rate measurements were performed on a number of alloys in high-pressure hydrogen and helium environments. The results of tensile tests performed in 34.5 MN/m2 (5000 psi) hydrogen indicated that Inconel 625 was considerable embrittled at ambient temperature but was not embrittled at 144 K (-200 F). The tensile properties of AISI 321 stainless steel were slightly reduced at ambient temperature and 144 K (-200 F). The tensile properties of Ti-5Al-2.5 Sn ELI were essentially unaffected by hydrogen at 144 K (-200 F). OFHC copper was not embrittled by hydrogen at ambient temperature or at 144 K (-200 F)

The Role of Dislocation Channeling in IASCC Initiation of Neutron Irradiated Austenitic Stainless Steel.

The objective of this study was to understand the role of dislocation channeling in the initiation of irradiation-assisted stress corrosion cracking (IASCC) of neutron irradiated austenitic stainless steel using a novel four-point bend test. Stainless steels used in this study were irradiated in the BOR-60 fast reactor at 320 °C, and included a commercial purity 304L stainless steel irradiated to 5.5, 10.2, and 47.5 dpa, and two high purity stainless steels, Fe-18Cr-12Ni and Fe-18Cr-25Ni, irradiated to ~10 dpa. The four-point bend test produced the same relative IASCC susceptibility as constant extension rate tensile (CERT) experiments performed on the same irradiated alloys in boiling water reactor normal water chemistry. The cracking susceptibility of the CP 304L alloy was high at all irradiation dose levels, enhanced by the presence of MnS inclusions in the alloy microstructure, which dissolve in the NWC environment. Dissolution of the MnS inclusion results in formation of an oxide cap that occludes the inclusion site, creating a crevice condition with a high propensity for crack initiation. Crack initiation at these locations was induced by stress concentration at the intersecting grain boundary, resulting from the intersection of a discontinuous dislocation channels (DC). Stress to initiate an IASCC crack decreased with dose due earlier DC initiation. The HP Fe-18Cr-12Ni alloy had low susceptibility to IASCC, while the high Ni alloy exhibited no cracking susceptibility. The difference in susceptibility among these conditions was attributed to the propensity for DCs to transmit across grain boundaries, which controls stress accumulation at DC – grain boundary intersections.PhDMaterials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120848/1/kalejs_1.pd

NBS monograph

From Abstract: "This monograph reviews available information on the production, properties, and uses of high-purity and commercial forms of nickel, and on the properties and applications of its important alloys, both ferrous and non ferrous.

An investigation of the corrosion behaviour of a range of engineering materials in marine environments

This work represents an investigation of the corrosion behaviour of primarily high-grade alloys in marine environments. A range of marine conditions of varying severity has been considered and their effect on the electrochemical corrosion characteristics assessed. The study has utilised a range of electrochemical monitoring techniques, light and scanning electro microscopy and other surface techniques to assess the extent and morphology of corrosion attack under certain conditions. Principal components of the study include the effect of elevated temperature (up to 60oC) on corrosion initiation and propagation in static and high velocity impinging seawater. In addition, the effect of micro and macro fouling has been assessed using immersion tests and a hydrodynamic model. Continuation of the biological effects on corrosion looked at the effect of the presence and activity of Sulphate Reducing Bacteria (SRB) on corrosion mechanism. Correlations between accelerated laboratory tests and the real time behaviour of materials have been successfully made. Methods to counteract fouling often include the use of biocides and, in this study, the effect of high levels of hypochlorite dosing has been investigated. Mechanical and corrosion effects by liquid impact and by liquid-solid impact constitute a major part of this work and the use of electrochemical tests has enabled the proportions of weight loss on a given material attributed to corrosion, erosion and a synergistic factor to be elucidated. Several options exist to combat excessive deterioration due to mechanical wear. Two processes, shot-peening and laser irradiation, have been assessed primarily for corrosion resistance in a marine environment

Metallurgy Division SemiAnnual Progress Report for Period Ending October 10, 1955

Static corrosion tests in sodium and in fused-fluoride-salt mixture on type 310 stainless steel T-joints brazed with various alloys by the Wall Colmonoy Corporation indicate that the 9% Si-2.5% P-88.5% Ni alloy has fair resistance to both media