Zum Mechanismus der chloridinduzierten Spannungsrisskorrosion hochlegierter austenitischer Stähle

Translated title of the contribution: On the Mechanism of Chloride Induced Stress Corrosion Cracking of Highly Alloyed Austenitic Stainless Steels

Stefan Holzleitner

Research output: ThesisDoctoral Thesis

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Abstract

Stress Corrosion Cracking (SCC) is often noticed as an embrittlement phenomenon on ductile materials. Interactions between the environment and the mechanical stresses in the material initiate a fracture with little deformation, which can lead to a sudden and catastrophic failure. Due to this fact SCC has been of technical and scientific interest since decades. Within this work a literature search concerning the mechanisms of chloride induced, transgranular SCC on austenitic stainless steels was conducted and the existing models were discussed. The discussion of the models showed, that SCC is an interaction between media and material specific conditions, which in sum generate the SCC initiating mechano-chemical synergy effect. Investigations on two different austenitic CrNi- and CrMnN-steels using various method approaches were carried out to identify the rate determining process. The results showed, that independent from the actual mechanism the kinetics of the anodic dissolution is the main influencing factor for both SCC initiation and crack propagation. For SCC initiation a certain plastic deformation is required, which is at about 90 +/- 10 % of 0.2 % yield strength of the material. This critical load is slightly depending on the corrosiveness of the medium. CrMnN-steels showed a higher dissolution rate and decreased repassivation abilities compared to the CrNi-steels. This is accompanied by a short incubation time and accelerated crack propagation if the critical load is exceeded. Due to the higher yield strength of the CrMnN-steels the absolute critical load in the solution annealed condition is higher for these steels than for CrNi-austenites. The electrochemically generated and from the steel absorbed hydrogen has a decisive influence on the local deformation behaviour and the electrochemical properties of the near crack tip zone. The suggested model is a mechano-chemical synergy effect of anodic dissolution and enhanced gliding processes influenced by hydrogen absorption.
Translated title of the contributionOn the Mechanism of Chloride Induced Stress Corrosion Cracking of Highly Alloyed Austenitic Stainless Steels
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
  • Pippan, Reinhard, Assessor B (internal)
  • Mori, Gregor Karl, Assessor A (internal)
Publication statusPublished - 2008

Bibliographical note

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Keywords

  • chloride induced SCC
  • austenitic stainless steels
  • SCC model

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