Analysis of stress corrosion cracking in X80 pipeline steel: An approach from the Theory of Critical Distances

This paper presents an analysis of Stress Corrosion Cracking (SCC) based on the Theory of Critical Distances (TCD). The research is based on an experimental program composed of fracture specimens with notch radius varying from 0 mm (crack-like defect) up to 1 mm, and tensile specimens. A pipeline steel was used in this work (X80). It has been analysed in one hydrogen embrittlement situation. The study has been completed with Finite Elements Simulation analysis. The capacity of the TCD to analyse SCC processes has been proven.The authors of this paper would like to thank the Spanish Ministry of Economy and Competitivity for the support received for the research project MAT2014-58738-C3-3-R developed by the University of Cantabria

The role of the testing rate on Small Punch tests for the estimation of fracture toughness in hydrogen embrittlement

ABSTRACT: In this paper, different techniques to test notched Small Punch (SPT) samples in fracture conditions in aggressive environments are studied, based on the comparison of the micromechanisms at different rates. Pre-embrittled samples subsequently tested in air at rates conventionally employed (0.01 and 0.002 mm/s) are compared to embrittled ones tested in environment at the same rates (0.01 and 0.002 mm/s) and at a very slow rate (5E-5 mm/s). A set of samples tested in environment under a set of constant loads that produce very slow rates completes the experimental results. As a conclusion, it is recommended to test SPT notched specimens in environment at very slow rates, of around E-6 mm/s, when characterizing in Hydrogen Embrittlement (HE) scenarios, in order to allow the interaction material-environment to govern the process

Ion beam analysis of as-received, H-implanted and post implanted annealed fusion steels

The elemental distribution for as-received (AR), H implanted (AI) and post-implanted annealed (A) Eurofer and ODS-Eurofer steels has been characterized by means of micro Particle Induced X-ray Emission (μ-PIXE), micro Elastic Recoil Detection (μ-ERD) and Secondary Ion Mass Spectrometry (SIMS). The temperature and time-induced H diffusion has been analyzed by Resonance Nuclear Reaction Analysis (RNRA), Thermal Desorption Spectroscopy (TDS), ERDA and SIMS techniques. μ-PIXE measurements point out the presence of inhomogeneities in the Y distribution for ODS-Eurofer samples. RNRA and SIMS experiments evidence that hydrogen easily outdiffuses in these steels even at room temperature. ERD data show that annealing at temperatures as low as 300 °C strongly accelerates the hydrogen diffusion process, driving out up to the 90% of the initial hydrogen

Using Small Punch tests in environment under static load for fracture toughness estimation in hydrogen embrittlement

In this paper, the response of three medium and high-strength steels to hydrogen embrittlement is analyzed by means of the quasi-non-destructive test known as the Small Punch Test (SPT). SPT tests on notched specimens under static load are carried out, applying Lacaclle's methodology to estimate the fracture toughness for crack initiation, comparing the results to KIEAC fracture toughness obtained from C(T) precracked specimens tested in the same environment; SPT showed good correlation to standard tests. A novel expression was proposed to define the parameter KIEAC-SP as the suitable one to estimate the fracture toughness for crack initiation in hydrogen embrittlement conditions by Small Punch means, obtaining good accuracy in its estimations. Finally, Slow Rate Small Punch Tests (SRSPT) are proposed as a more efficient alternative, introducing an order of magnitude for the adequate rate to be employed

Cracks in Martensite Plates as Hydrogen Traps in a Bearing Steel

It is demonstrated that a macroscopically homogeneous distribution of tiny cracks introduced into a martensitic bearing steel sample can provide powerful hydrogen traps. The phenomenon has been investigated through thermal desorption spectroscopy and hydrogen permeation measurements using both cracked and integral samples. The e↵ective hydrogen di↵usion coefficient through the cracked sample is found to be far less than in the uncracked one. Similarly, when samples are charged with hydrogen, and then subjected to thermal desorption analysis, the amount of hydrogen liberated from the cracked sample is smaller due to the trapping by the cracks. Theoretical analysis of the data shows that the traps due to cracks are so strong, that any hydrogen within the cracks can never in practice de-trap and cause harm by mechanisms that require the hydrogen to be mobile for the onset of embrittlement.W. Solano-Alvarez is very grateful for support from the Worshipful Company of Ironmongers, CONACyT, the Cambridge Overseas Trust, and the Roberto Rocca Education Programme.This is the accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s11661-014-2680-8

Effects of annealing treatment prior to cold rolling on delayed fracture properties in ferrite-austenite duplex lightweight steels

Tensile properties of recently developed automotive high-strength steels containing about 10 wt pct of Mn and Al are superior to other conventional steels, but the active commercialization has been postponed because they are often subjected to cracking during formation or to the delayed fracture after formation. Here, the delayed fracture behavior of a ferrite-austenite duplex lightweight steel whose microstructure was modified by a batch annealing treatment at 1023 K (750 A degrees C) prior to cold rolling was examined by HCl immersion tests of cup specimens, and was compared with that of an unmodified steel. After the batch annealing, band structures were almost decomposed as strong textures of {100}aOE (c) 011 > alpha-fibers and {111}aOE (c) 112 > gamma-fibers were considerably dissolved, while ferrite grains were refined. The steel cup specimen having this modified microstructure was not cracked when immersed in an HCl solution for 18 days, whereas the specimen having unmodified microstructure underwent the delayed fracture within 1 day. This time delayed fracture was more critically affected by difference in deformation characteristics such as martensitic transformation and deformation inhomogeneity induced from concentration of residual stress or plastic strain, rather than the difference in initial microstructures. The present work gives a promise for automotive applications requiring excellent mechanical and delayed fracture properties as well as reduced specific weight.ope

Le tympan de Strzelno

Preyssoure Léon. Le tympan de Strzelno. In: Bulletin Monumental, tome 125, n°2, année 1967. pp. 202-203

L'Ézéchiel de Mont-devant-Sassey

Pressouyre Léon. L'Ézéchiel de Mont-devant-Sassey. In: Bulletin de la Société Nationale des Antiquaires de France, 1970, 1972. pp. 98-108