Cracking Mechanisms of Hot-Dip Galvannealed Coatings on CP1000 Steel

2019 ◽  
pp. 559-565
Author(s):  
Huasai Liu ◽  
Libin Liu ◽  
Haiquan Wang ◽  
Yun Han ◽  
Chunqian Xie ◽  
...  
Keyword(s):  
Cracking Mechanisms

Micromechanisms of Hydrogen-Assisted Cracking in Super Duplex Stainless Steel Investigated by Scanning Probe Microscopy

2014 ◽  
Author(s):  
Bai An ◽  
Takashi Iijima ◽  
Chris San Marchi ◽  
Brian Somerday
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Scanning Tunneling ◽  
Super Duplex Stainless Steel ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Hydrogen Assisted Cracking ◽  
Cracking Mechanisms ◽  
Localized Plastic Deformation

Understanding the micromechanisms of hydrogen-assisted fracture in multiphase metals is of great scientific and engineering importance. By using a combination of scanning electron microscopy (SEM), scanning tunneling microscopy (STM), atomic force microscopy (AFM) and magnetic force microscopy (MFM), the micromorphology of fracture surface and microcrack formation in hydrogen-precharged super duplex stainless steel 2507 are characterized from microscale to nanoscale. The results reveal that the fracture surfaces consist of quasi-brittle facets with riverlike patterns at the microscale, which exhibit rough irregular patterns or remarkable quasi-periodic corrugation patterns at the nanoscale that can be correlated with highly localized plastic deformation. The microcracks preferentially initiate and propagate in ferrite phase and are stopped or deflected by the boundaries of the austenite phase. The hydrogen-assisted cracking mechanisms in super duplex stainless steel are discussed according to the experimental results and hydrogen-enhanced localized plasticity theory.

scholarly journals Effect of pH on Stress Corrosion Cracking of 6082 Al Alloy

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 578 ◽  
Author(s):  
C. Panagopoulos ◽  
Emmanuel Georgiou ◽  
K. Giannakopoulos ◽  
P. Orfanos
Keyword(s):  
Aluminum Alloy ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Al Alloy ◽  
Cracking Behavior ◽  
Effect Of Ph ◽  
Cracking Mechanisms ◽  
6082 Aluminum Alloy ◽  
6082 Al Alloy

In this work, the effect of pH (3, 7 and 10) on the stress corrosion cracking behavior of 6082 aluminum alloy, in a 0.3 M sodium chloride (NaCl) aqueous based solution was investigated. The stress corrosion cracking behavior was studied with slow strain rate testing, whereas failure analysis of the fractured surfaces was used to identify the dominant degradation mechanisms. The experimental results clearly indicated that stress corrosion cracking behavior of this aluminum alloy strongly depends on the pH of the solution. In particular, the highest drop in ultimate tensile strength and ductility was observed for the alkaline pH, followed by the acidic, whereas the lowest susceptibility was observed in the neutral pH environment. This observation is attributed to a change in the dominant stress corrosion cracking mechanisms.

In-Service Cracking/Leak at Bottom-Side Repaired Dent

2020 ◽  
Author(s):  
Gregory T. Quickel ◽  
Joseph Bratton ◽  
William A. Bruce
Keyword(s):  
Laser Scanning ◽  
Current Knowledge ◽  
Service Failure ◽  
Fatigue Behavior ◽  
Crack Identification ◽  
Repair Method ◽  
Cracking Mechanisms ◽  
Bottom Side ◽  
Non Destructive

Abstract Pipeline operators are often faced with excavating deformations caused by bottom-side indenters (e.g., rock dents). These dents are typically constrained by the rock, but during excavation, after the rock is removed, the dent is no longer constrained. Many operators have felt that it is prudent to perform in-the-ditch (ITD) non-destructive examination (NDE) techniques, such as liquid penetrant testing (LPT) and magnetic particle inspection (MPI), to determine if external cracking is present so that an appropriate repair method can be selected. Unfortunately, these external surface NDE methods do not identify the presence of internal cracking. Recent research [1], along with metallurgical analyses of cracks at bottom-side dents, demonstrates that the fatigue behavior of constrained dents is different than that of unconstrained dents, and that identifying the correct crack mechanism can be difficult. The paper discusses cracking mechanisms (e.g., stress corrosion cracking, fatigue, etc.) at bottom-side dents, ITD crack identification methods, differences between constrained and non-constrained dents, repair methods for dents, and presents a case study that uses NDE (MPI, unconventional LPT, and laser scanning) and destructive techniques (metallography, fractography, and hardness testing) to determine the metallurgical cause of a failure. The case study involves a pre-formed composite sleeve system that was used to repair dents in which correct installation procedures were followed but ultimately resulted in a delayed in-service failure. In hindsight, if ITD NDE methods were chosen based on our current knowledge of recent research, the operator may have been aware of the presence of cracking and selected a different repair method, and therefore would have likely prevented an in-service failure. This paper provides a case study to help increase awareness regarding how to properly evaluate cracking in dents. Operators should ensure that their excavation and repair procedures are updated to reflect the most current industry knowledge to help prevent a similar failure.

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