Influence of heterocyclic nitrogenous bases contained in a hydrogen sulfide medium on the kinetics of corrosion fatigue cracks in 40Kh steel

The approach for determining the residual life of the vehicles’ thin-walled metal elements with cracks under the action of cyclic loads and corrosive environment is developed based on the first law of thermodynamics and the fracture mechanics principles. Based on the results of the mathematical description of electrochemical reactions and separate data of fracture mechanics, the equation describing the kinetics of the corrosion-fatigue cracks propagation is deduced. This equation and the initial and final conditions are a mathematical model for determining the residual life of structural elements. The correctness of the developed analytical models is confirmed by the experimental data known in the literature. The performance of this model is demonstrated on the example of determining the residual life of a plate made of 17G1S steel. The plate was diluted by a crack in a 3% NaCl solution and subjected to cyclic loading. An increase in the initial size of corrosion-fatigue cracks is significant to reduce the period of their subcritical growth.

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Effect of strain frequency on development of corrosion-fatigue cracks in 08KP steel

Soviet Materials Science ◽

10.1007/bf00715148 ◽

1975 ◽

Vol 10 (3) ◽

pp. 345-346

Author(s):

M. O. Levitskii

Keyword(s):

Corrosion Fatigue ◽

Fatigue Cracks ◽

08Kp Steel ◽

Strain Frequency

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Lifetime Enhancement of Propulsion Shafts Against Corrosion-Fatigue by Laser Peening

10.5957/pss-2018-01 ◽

2018 ◽

Author(s):

Lloyd A. Hackel ◽

Jon E. Rankin

Keyword(s):

Corrosion Fatigue ◽

Fatigue Testing ◽

Salt Water ◽

Fatigue Cracks ◽

Water Immersion ◽

High Energy ◽

General Corrosion ◽

Laser Peening ◽

Corrosion Pits ◽

Deep Pits

This paper reports substantially enhanced fatigue and corrosion-fatigue lifetimes of propulsion shaft materials, 23284A steel and 23284A steel with In625 weld overlay cladding, as a result of shot or laser peening. Glass reinforced plastic (GRP) coatings and Inconel claddings are used to protect shafts against general corrosion and corrosion pitting. However salt water leakage penetrating under a GRP can actually enhance pitting leading to crack initiation and growth. Fatigue coupons, untreated and with shot or laser peening were tested, including with simultaneous salt water immersion. Controlled corrosion of the surfaces was simulated with electric discharge machining (EDM) of deep pits enabling evaluation of fatigue and corrosion-fatigue lifetimes. Results specifically show high energy laser peening (HELP) to be a superior solution, improving corrosion-fatigue resistance of shaft and cladding metal, reducing the potential for corrosion pits to initiate fatigue cracks and dramatically slowing crack growth rates. At a heavy loading of 110% of the 23284A steel yield stress and with 0.020 inch deep pits, laser peening increased fatigue life of the steel by 1370% and by 350% in the corrosion-fatigue testing.

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