scholarly journals Comparison of the microstructure, deformation and crack initiation behavior of austenitic stainless steel irradiated in-reactor or with protons

2015 ◽  
Vol 456 ◽  
pp. 85-98 ◽  
Author(s):  
Kale J. Stephenson ◽  
Gary S. Was
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Crack Initiation

scholarly journals Toward consistent fatigue crack initiation criteria for 304L austenitic stainless steel under multi-axial loads

2015 ◽  
Vol 75 ◽  
pp. 57-68 ◽  
Author(s):  
Bai-Mao Lei ◽  
Van-Xuan Tran ◽  
Saïd Taheri ◽  
Jean-Christophe le Roux ◽  
François Curtit ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Austenitic Stainless Steel ◽  
Crack Initiation ◽  
Fatigue Crack Initiation ◽  
Axial Loads

Thermal and Mechanical Fatigue Loading: Mechanisms of Crack Initiation and Crack Growth

2014 ◽  
Author(s):  
Stefan Utz ◽  
Ewa Soppa ◽  
Christopher Kohler ◽  
Xaver Schuler ◽  
Horst Silcher
Keyword(s):  
Stainless Steel ◽  
Cyclic Loading ◽  
Austenitic Stainless Steel ◽  
Crack Initiation ◽  
Crack Growth ◽  
Mechanical Loading ◽  
Room Temperature ◽  
Fatigue Behaviour ◽  
Stress And Strain ◽  
Micro Cracks

The present contribution is focused on the experimental investigations and numerical simulations of the deformation behaviour and crack development in the austenitic stainless steel X6CrNiNb18-10 (AISI–347) under thermal and mechanical cyclic loading in HCF and LCF regimes. The main objective of this research is the understanding of the basic mechanisms of fatigue damage and development of simulation methods, which can be applied further in safety evaluations of nuclear power plant components. In this context the modelling of crack initiation and crack growth inside the material structure induced by varying thermal or mechanical loads are of particular interest. The mechanisms of crack initiation depend among other things on the art of loading, microstructure, material properties and temperature. The Nb-stabilized austenitic stainless steel in the solution-annealed condition was chosen for the investigations. Experiments with two kinds of cyclic loading — pure thermal and pure mechanical — were carried out and simulated. The fatigue behaviour of the steel X6CrNiNb18-10 under thermal loading was studied within the framework of the joint research project [1]. Interrupted thermal cyclic tests in the temperature range of 150 °C to 300 °C combined with non-destructive residual stress measurements (XRD) and various microscopic investigations, e.g. in SEM, were used to study the effects of thermal cyclic loading on the material. This thermal cyclic loading leads to thermal induced stresses and strains. As a result intrusions and extrusions appear inside the grains (at the surface), at which micro-cracks arise and evolve to a dominant crack. Finally, these micro-cracks cause continuous and significant decrease of residual stresses. The fatigue behaviour of the steel X6CrNiNb18-10 under mechanical loading at room temperature was studied in the framework of the research project [2]. With a combination of interrupted LCF tests and EBSD measurements the deformation induced transformation of a fcc austenite into a bcc α′-martensite was observed in different stages of the specimen lifetime. The plastic zones develop at the crack tips, in which stress and strain amplitudes are much higher than the nominal loading, and enable martensitic transformation in the surrounding of the crack tip. The consequence of this is that cracks grow in the “martensitic tunnels”. The short and long crack growth behaviours of the steel X6CrNiNb18-10 under mechanical loading at room temperature and T = 288 °C were studied for different loading parameters. Moreover, the R-ratio was modified in order to study the effect of crack closure at the crack tip for long cracks. Several FE-models of specimens with different geometries and microstructures were created and cyclically loaded according to the experimental boundary conditions. A plastic constitutive law based on a Chaboche type model was implemented as a user subroutine in the FE software ABAQUS. The corresponding material parameters were identified using uniaxial LCF tests of X6CrNiNb18-10 with different strain amplitudes and at different temperatures. These calculations aimed in the estimation of stress and strain distributions in the critical areas in which the crack initiation was expected.

Initiation of Stress Corrosion Cracking; Migration of Chloride in Oxide Films on Austenitic Stainless Steel

CORROSION ◽  
1964 ◽  
Vol 20 (9) ◽  
pp. 269t-274t ◽  
Author(s):  
C. R. BERGEN
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Crack Initiation ◽  
Tensile Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Base Alloy ◽  
Corrosion Cracking ◽  
Stress Cracking ◽  
High Nickel

Abstract The mechanism of stress corrosion crack initiation can perhaps be understood by noticing the similarities among the several corrodent-crack susceptible alloy systems. In a number of such systems the specific ion responsible for cracking is relatively large. The corrosion product formed in a corroding medium containing such ions would imbibe them. Under appropriate conditions, due to their size, the larger ions would tend to diffuse to the region of the oxide film under highest tensile stress where local high tensile stress in the base alloy would be reflected. It is postulated that the appropriate conditions for diffusion are present in stress cracking systems and that the migration of the ion to which cracking is ascribed leads to high local concentrations in turn causing a local increase in corrosivity. Where the physical properties of the alloy are such that crack propagation can occur, stress corrosion cracking results. Tests of the above hypothesis have been conducted with the chloride-austenitic stainless steel system. It was shown that chloride will migrate reversibly under the influence of tensile stress. It was also shown that the presence of nickel will inhibit the migration of chloride up a tensile gradient and the immunity to cracking of high nickel austenitic stainless alloys is attributed to this effect.

Sign in / Sign up

Export Citation Format

Share Document