Oxide Film Characterization after the crack propagation in CT specimens of AISI 304L under Hydrogen Water Chemistry Condition.

2016 ◽  
Vol 1814 ◽  
Author(s):  
Ángeles Díaz Sánchez ◽  
Aida Contreras Ramírez ◽  
Carlos Arganis Juárez
Keyword(s):  
Oxide Film ◽  
Crack Propagation ◽  
Water Chemistry ◽  
Degradation Mechanism ◽  
Electrochemical Corrosion ◽  
General Term ◽  
Test Method ◽  
Feed Water ◽  
Aisi 304L ◽  
Hydrogen Water

ABSTRACTStress Corrosion Cracking (SCC) in a general term describing stressed alloy fracture that occurs by crack propagation in specifically environments, and has the appearance of brittle fracture, yet it can occur in ductile materials like AISI 304L used in internal components of Boiling Water Reactors (BWR). The high levels of oxygen and hydrogen peroxide generated during an operational Normal Water Condition (NWC) promotes an Electrochemical Corrosion Potential (ECP), enough to generate SCC in susceptible materials. Changes in water chemistry have been some of the main solutions for mitigate this degradation mechanism, and one of these changes is reducing the ECP by the injection of Hydrogen in the feed water of the reactor; this addition moves the ECP below a threshold value, under which the SCC is mitigated (-230mV vs SHE). This paper shows the characterization by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Raman Spectroscopy of the oxide film formed in to a crack propagated during a Rising Displacement Test method (RDT), on Hydrogen Water Chemistry (HWC) conditions: 20 ppb O2, 125 ppb H2, P=8MPa, T=288°C, using a CT specimen of austenitic stainless steel AISI 304L sensitized. The characterization allowed identifying the magnetite formation since an incipient way, until very good formed magnetite crystals.

Interfacial Fracture Characterization of Nano-Scale Thin Films Using Single-Strip Stress-Engineered Superlayer

2006 ◽  
Author(s):  
Jiantao Zheng ◽  
Suresh K. Sitaraman
Keyword(s):  
Thin Films ◽  
Crack Propagation ◽  
Interfacial Crack ◽  
Interfacial Fracture ◽  
Critical Energy ◽  
Test Method ◽  
Nano Scale ◽  
Available Energy ◽  
Fracture Parameters

Characterization of interfacial fracture parameters for nano-scale thin films continues to be challenging due to the difficulties associated with preparing samples, fixturing and loading the samples, and extracting and analyzing the experimental data. In this paper, we propose a stress-engineered superlayer test method that can be used to measure the interfacial fracture parameters of nano-scale (as well as micro-scale) thin films without the need for loading fixtures. The proposed test employs the residual stress in sputter-deposited metals to provide the energy for interfacial crack propagation. The innovative aspect of the test is the use of an etchable release layer that is deposited between the two interfacial materials of interest. The release layer is designed such that the available energy for interfacial crack propagation will continue to decrease as the crack propagates, and at the location where the crack ceases to propagate, the available energy for crack propagation will be the critical energy for crack propagation or the interfacial fracture toughness. The proposed test method has been successfully used to characterize Ti thin film on Si substrate.

Slow Crack Growth in Dental Composites

1985 ◽  
Vol 55 ◽  
Author(s):  
G. M. Montes-G. ◽  
R. A. Draughn ◽  
T. H. Simpson
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Slow Crack Growth ◽  
High Stress ◽  
Torsion Test ◽  
Stable Crack Growth ◽  
Test Method ◽  
Volume Percent ◽  
Stick Slip ◽  
Model Composite

ABSTRACTThe fracture properties of selected commercial composite dental restorative materials and a model composite system were studied to determine the influences of the reinforcing phase, exposure to water, and particle/polymer adhesion on crack propagation. The content of inorganic fillers ranged from 36 to 62 volume percent. In the model system the polymer phase approximated that of the commercial products, a constant size distribution of quartz fillers was used, and polymer/particle adhesion was varied. The double torsion test method was employed to measure relationships between applied stress intensity factor and velocity of crack propagation during stable crack growth. In all systems, cracks propagated through regions of high stress concentration at the low end of the velocity range studied (10−7 m/sec to 10−3 m/sec). Wet materials fractured at lower stress intensities than dry materials at all velocities. At high velocities unstable (stick-slip) growth occurred in dry materials with strong filler/matrix interfaces and in wet specimens with initially strong interfaces and less than 41 volume percent filler. In wet conditions, materials with poorly bonded fillers fractured by slow crack growth at stress intensities 10% to 30% below the levels of composites with strong interfaces.

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