Rissfortschrittsmessungen an Stickstoff legierten austenitischen rostfreien Stählen unter korrosiven Bedingungen

Translated title of the contribution: Crack growth rate measurements on nitrogen alloyed austenitic stainless steels in corrosive media

Clemens Vichytil

Research output: ThesisDiploma Thesis


Crack growth rate curves can be measured precisely in inert and aggressive aqueous media at elevated temperatures with the developed assembly. Crack growth rate versus cyclic stress intensity curves were measured in inert glycerin and in 62% CaCl2 solution respectively. The investigated materials were a CrMnN and a CrNiMoN stabilized austenitic stainless steel. Both steels were investigated in solution annealed condition. Additionally cyclic polarization curves have been recorded. These measurements showed that the steel P553 has no passive range compared to the steel A975. Comparing the crack growth rates it is indicated that the threshold value for long crack growth is decreased at both materials in corrosive environment. Furthermore crack growth rates for steel P556 are significantly increased in aggressive media. This effect is due to general corrosive attack as well as to stress corrosion cracking. Cl- induced stress corrosion cracking was found on the specimens surface. General corrosive attack is enabled through slip bands which penetrate the passive layer of the material. The steel P556 moreover is susceptible to pitting and filiform corrosion. The threshold for long crack growth is significantly decreased at the steel A975, but no increase in crack growth was observed. Crack growth rates in inert and corrosive media are almost the same. No susceptibility to stress corrosion cracking was encountered. Due to the wide passive range of this steel no corrosive attack was observed. Fractographic investigations in a scanning electron microscope revealed transgranular fatigue cracks with some intergranular parts at both materials. The amount of slip steps on the surface of the specimens is increased with expanding crack length. Striations get coarser with increasing crack length, which is accompanied with faster crack growth and increasing loading of the crack tip. Furthermore cleavage cracks and facetted fracture surfaces with factory roof structure, which are a sign for stress corrosion cracking, were found investigating the steel P556.
Translated title of the contributionCrack growth rate measurements on nitrogen alloyed austenitic stainless steels in corrosive media
Original languageGerman
  • Mori, Gregor Karl, Supervisor (internal)
Award date18 Dec 2009
Publication statusPublished - 2009

Bibliographical note

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  • Corrosion fatigue nitrogen alloyed austenites crack growth rate fracture mechanics

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