【Corrosion Technology Edition】Daily Question 20170824: What are the characteristics of stress corrosion cracking?

(1) What causes stress corrosion failure is a static stress, which is much lower than the yield strength of the material, and it is generally a tensile stress. (2) Damage caused by stress corrosion is brittle fracture, with no significant plastic deformation. (3) Stress corrosion occurs only when specific alloy compositions are combined with specific media. (4) The crack growth rate in stress corrosion is generally between 10-9 and 10-6 m/s; it is somewhat similar to fatigue, being gradual and slow. This subcritical growth continues until a certain critical size is reached, at which point the remaining cross-section can no longer withstand external loads, leading to sudden fracture. (5) Cracks caused by stress corrosion generally originate from surface pits, and the propagation direction of these cracks is often perpendicular to the tensile axis. (6) The fracture surface of stress corrosion failure is dull in color, with corrosion products often present on its surface. (7) The main crack propagation in stress corrosion often exhibits branching. (8) Fracture caused by stress corrosion can be transgranular or intergranular.

1. Stress corrosion failure is caused by static stress, which is much lower than the yield strength of the material, and it is generally a tensile stress. 2. Damage caused by stress corrosion is a brittle fracture, with no significant plastic deformation. 3. Stress corrosion occurs only when specific alloy compositions are combined with specific media. 4. The crack growth rate in stress corrosion is generally between 10-9 and 10-6 m/s; it is somewhat similar to fatigue, being a gradual and slow process. This subcritical growth continues until a certain critical size is reached, at which point the remaining cross-section can no longer withstand external loads, leading to sudden fracture. 5. Cracks resulting from stress corrosion usually originate from surface pits, and the propagation direction of these cracks is often perpendicular to the tensile axis. 6. The fracture surface of stress corrosion failure is dull in color, with corrosion products often present on its surface. 7. The main crack propagation in stress corrosion often exhibits branching. 8. Fracture caused by stress corrosion can be transgranular or intergranular.

Stress must be present, especially the tensile stress component； The system is specific; stress corrosion cracking occurs only in certain combinations of metals and media ； The fracture surface of stress corrosion cracking is generally of a brittle fracture type, with no prior signs before failure, which makes it extremely hazardous.

(1) What causes stress corrosion failure is a static stress, which is much lower than the yield strength of the material, and it is generally a tensile stress. (2) Damage caused by stress corrosion is brittle fracture, with no significant plastic deformation. (3) Stress corrosion occurs only when specific alloy compositions are combined with specific media. (4) The crack growth rate in stress corrosion is generally between 10-9 and 10-6 m/s; it is somewhat similar to fatigue, being gradual and slow. This subcritical growth continues until a certain critical size is reached, at which point the remaining cross-section can no longer withstand external loads, leading to sudden fracture. (5) Cracks caused by stress corrosion generally originate from surface pits, and the propagation direction of these cracks is often perpendicular to the tensile axis. (6) The fracture surface of stress corrosion failure is dull in color, with corrosion products often present on its surface. (7) The main crack propagation in stress corrosion often exhibits branching. (8) Fracture caused by stress corrosion can be transgranular or intergranular.

The presence of stress, particularly the tensile stress component； The system is specific; stress corrosion cracking occurs only in certain combinations of metals and media ； The fracture surface of stress corrosion cracking is generally of a brittle fracture type, with no prior signs before failure, which makes it extremely hazardous.

(1) What causes stress corrosion failure is a static stress, which is much lower than the yield strength of the material, and it is generally a tensile stress. (2) Damage caused by stress corrosion is brittle fracture, with no significant plastic deformation. (3) Stress corrosion occurs only when specific alloy compositions are combined with specific media. (4) The crack growth rate in stress corrosion is generally between 10-9 and 10-6 m/s; it is somewhat similar to fatigue, being gradual and slow. This subcritical growth continues until a certain critical size is reached, at which point the remaining cross-section can no longer withstand external loads, leading to sudden fracture. (5) Cracks caused by stress corrosion generally originate from surface pits, and the propagation direction of these cracks is often perpendicular to the tensile axis. (6) The fracture surface of stress corrosion failure is dull in color, with corrosion products often present on its surface. (7) The main crack propagation in stress corrosion often exhibits branching. (8) Fracture caused by stress corrosion can be transgranular or intergranular.

1) Stress corrosion failure is caused by static stress, which is much lower than the yield strength of the material, and it is generally a tensile stress. (2) Damage caused by stress corrosion is brittle fracture, with no significant plastic deformation. (3) Stress corrosion occurs only when specific alloy compositions are combined with specific media. (4) The crack growth rate in stress corrosion is generally between 10-9 and 10-6 m/s; it is somewhat similar to fatigue, being gradual and slow. This subcritical growth continues until a certain critical size is reached, at which point the remaining cross-section can no longer withstand external loads, leading to sudden fracture. (5) Cracks caused by stress corrosion generally originate from surface pits, and the propagation direction of these cracks is often perpendicular to the tensile axis. (6) The fracture surface of stress corrosion failure is dull in color, with corrosion products often present on its surface. (7) The main crack propagation in stress corrosion often exhibits branching. (8) Fracture caused by stress corrosion can be transgranular or intergranular.

(1) What causes stress corrosion failure is a static stress, which is much lower than the yield strength of the material, and it is generally a tensile stress. (2) Damage caused by stress corrosion is brittle fracture, with no significant plastic deformation. (3) Stress corrosion occurs only when specific alloy compositions are combined with specific media. (4) The crack growth rate in stress corrosion is generally between 10-9 and 10-6 m/s; it is somewhat similar to fatigue, being gradual and slow. This subcritical growth continues until a certain critical size is reached, at which point the remaining cross-section can no longer withstand external loads, leading to sudden fracture. (5) Cracks caused by stress corrosion generally originate from surface pits, and the propagation direction of these cracks is often perpendicular to the tensile axis. (6) The fracture surface of stress corrosion failure is dull in color, with corrosion products often present on its surface. (7) The main crack propagation in stress corrosion often exhibits branching. (8) Fracture caused by stress corrosion can be transgranular or intergranular.

1. The conditions for stress corrosion are, first, tensile stress, and second, a stress-corrosion environment (including temperature and corrosive media).    2. The hazard lies in the fact that fracture caused by stress corrosion occurs without any obvious macroscopic deformation or prior signs, and the failure is sudden. Cracks often extend deep into the metal, and once they occur, they are difficult to repair; sometimes the entire device has to be discarded. Due to the complex nature of stress corrosion cracks, which involve many different scientific fields, many issues remain unresolved to this day.    3. In terms of their macroscopic appearance, stress corrosion cracks occur only on the metal surface in contact with the corrosive medium, and then extend from that surface inward. Visually, these cracks take on various forms such as linear, dendritic, cracked, or radial shapes; however, no significant plastic deformation is observed. The direction of the cracks is perpendicular to the tensile stress applied. From a microstructural perspective, the stress corrosion cracks that penetrate deep into the metal appear as dried-up tree roots, with thin, branched “roots”; as shown in the figure below, the fracture surfaces of these cracks are typical of brittle fractures

Stress corrosion cracking refers to the brittle fracture of metal materials under tensile stress, in certain specific environmental conditions, as a result of the combined effect of corrosion and stress.