Got it Cracked?

Developments in Corrosion Protection, 2014

The author als o wis h es to express his appreciation to Dr. Jerome Kruger. of the Nation al Bureau of Standards , and to the other NBS personne l , for their kind assistance in the publication of this volume.

MultiScience - XXXIII. microCAD International Multidisciplinary Scientific Conference, 2019

The International Journal of Advanced Manufacturing Technology

Stress corrosion cracking (SCC) is a phenomenon in which the cracking of a metal alloy usually results from the combined action of a corrodent and tensile stress. Stresses that cause cracking can be residual or may be applied during service. A degree of mechanistic understanding of SCC will enable most metallic engineering materials to operate safely though stress corrosion cracking failures still continue to occur unexpectedly in industry. In this paper, the characteristics, mechanisms and methods of SCC prevention are reviewed. The results of experimental studies on alpha brass are also reported of which the failure mode conformed with the film-rupture and anodic dissolution mechanism.

Two-dimensional and three-dimensional crack morphologies of stress corrosion cracking (SCC) were studied by serial-sectioning and synchrotron-based X-ray computed tomography. Discontinuous surface cracks were actually continuous inside the specimen, which matched typical river-like fractographs and finite element simulations. A low stress SCC model was created, where a main crack continuously grew along the main propagation direction (MPD) due to anodic dissolution; then, discontinuous secondary microcracks emanated from MPD, angularly extending to the two sides of MPD. Finally, some of the secondary microcracks reached the sample surface, resulting in the formation of discontinuous surface cracks.

JOM, 1993

The interactions of composition, microstructure, and corrosion processes have been studied extensively. In stress-corrosion cracking (SeC)-where mechanical stresses can accelerate failure-material chemistry and microstructure can alter the corrosion attack as well as influence deformation and fracture. The mechanisms through which these effects are felt, however,do not apply universally and are often difficult to elucidate. This article reviews mechanisms wherein corrosion behavior is the main influence, examining how segregation and precipitation at grain boundaries affects intergranular Sec.

ASME PVP 2008, 2008

The development and validation of predictive models for intergranular stress corrosion cracking requires knowledge of short crack growth kinetics in response to mechanical driving forces. A new experimental method for in-situ observation of the early stages of crack growth during stress corrosion cracking, via full field Digital Image Correlation, is described and data for crack growth kinetics are presented. Intergranular stress corrosion cracks were nucleated in sensitised 304 stainless steel under static uniaxial flexural deflection, within a potassium tetrathionate environment. High resolution optical images of a 2mm by 2mm area are recorded through the test solution during the experiment. The raw images show no observable cracking. However, the high sensitivity of digital image correlation allows small crack opening displacements to be detected. The derived strain map of the sample surface thereby enables imaging of the cracks. Surface cracks with lengths exceeding approximately 30µm can be observed. Post processing of the strain maps is then used to track the development of the cracks

Laue diffraction measurements made using polychromatic synchrotron x-radiation have revealed significant changes to the microscopic strain distributions in an Alloy 600 (UNS N06600) tube following the application of a circumferential (hoop) stress and then as a result of stress corrosion cracking (SCC). The changes in the elastic and plastic strain distributions were studied for the same area near the outer diameter of the tube prepared as a C-ring. Following the application of the circumferential stress, there was a notable loss of crystal order within the outermost 3 µm to 5 µm of the tube surface as a result of plastic processes; further into the sample the elastic strains in grain boundaries become oriented toward the direction of the impressed stress. The average intensity of oriented tensile strain is 5×10 -3 within the outermost 50 µm of the C-ring. After corrosion, the elastic strain distribution in the same region becomes slightly compressive. The strains associated with a network of fine incipient cracks on the outside diameter of the C-ring were explored; elastic compressive strains were found within few micrometers from the crack center presumably as a result of crack opening, while plastic deformation was limited to the immediate crack region.

Environment-Induced Cracking of Materials, 2008

This paper presents high resolution X-ray tomographic observations of intergranular stress corrosion crack nucleation and growth. In-situ experiments have been performed on beam line ID19 at the European Synchrotron Radiation Facility (ESRF). High-resolution tomography provides non-destructive, three-dimensional information of the shape and depth of damage. To the authors' knowledge, these are the first such observations of stress corrosion, and demonstrate the potential for high resolution, synchrotron, X-ray tomography as a tool for observing pitting, intergranular corrosion and intergranular cracking.

Corrosion Science, 2014

Two-dimensional and three-dimensional crack morphologies of stress corrosion cracking (SCC) were studied by serial-sectioning and synchrotron-based X-ray computed tomography. Discontinuous surface cracks were actually continuous inside the specimen, which matched typical river-like fractographs and finite element simulations. A low stress SCC model was created, where a main crack continuously grew along the main propagation direction (MPD) due to anodic dissolution; then, discontinuous secondary microcracks emanated from MPD, angularly extending to the two sides of MPD. Finally, some of the secondary microcracks reached the sample surface, resulting in the formation of discontinuous surface cracks.

1994

LOG (i) 100uA imA Carbon steel scanned in lean gas 50°C, 18 bar. "'film free, D 30 hours.