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Problems of hydrogen interaction with metals and methods of structures lifetime estimation.

Kurzydłowski K., Nykyforchyn H.

Prace Naukowe Instytutu Materiałoznawstwa i Mechaniki Technicznej Politechniki Wrocławskiej. Konferencje

2007

Vol. 65, nr 11

55-69

The hydrogen induced degradation of the properties and microstructure of the low carbon low-alloyed steels due to exploitation and exposition to the hydrogenated environment at ambient and elevated temperatures have been considered. The essential decrease of mechanical (impact strength, creep), corrosion (corrosion rate) and corrosion-mechanical (stress corrosion cracking) properties of exploited metal to compare with that in the virgin state is demonstrated. Especially high sensitivity of an effective range of stress intensity factor of fatigue crack growth to in-service degradation is shown. Weld metal is more sensitive to hydrogen degradation and even tensile mechanical properties of strength and plasticity are sensitive enough to "in-bulk" material degradation. An approach to the residual life time evaluation of the power plant steam pipe lines is developed, which allows to take into account the negative hydrogen effect. Some electrochemical parameters are especially sensitive to in-service degradation of steels at high and low temperatures as well. A good correlation between changes of electrochemical and mechanical properties in the steel degradation process gives prospects for the development of NDT methods for evaluation of the current state of exploited steels. The results discussed show that inspection of the surfaces of installations to find corrosion or mechanical damage alone may not be sufficient for proper evaluating risk of failure.

Assessment of structural changes at IN-519 cast steel reformer tubes

Łabanowski J.

Advances in Materials Science

2005

Vol. 5, nr 1-3

14-20

Catalytic tubes are the most important parts in reformer furnaces at ammonia chemical plants. A steam reforming process converts hydrocarbons into mixtures of hydrogen, carbon monoxide and carbon dioxide. This reaction proceeds at a temperature range 800-900 °C and under pressure 3 - 4 MPa. This severe working condition causes a structural damage in the tubes. It is necessary to develop reliable methods for inspection of tube degradation and for realistic prediction of its residual life. The paper presents effects of long-term service at elevated temperatures on microstructural changes of the alloy IN-519 (24%Cr, 24%Ni, Nb).