Environment Induced Cracking of Turbine Disc Steel: Effect of Organic Acids on Corrosion Fatigue of 3.5NiCrMoV Steels in High Temperature Water

2007 ◽  
Vol 345-346 ◽  
pp. 999-1002
Author(s):  
W.Y. Maeng
Keyword(s):  
Growth Rate ◽  
Acetic Acid ◽  
High Temperature ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Rates ◽  
High Temperature Water ◽  
Turbine Disc ◽  
Crack Growth Rates ◽  
Temperature Water

Organic acids (acetic and formic acid) are produced by the decomposition of ETA (Ethanol Amine, C2H7NO) used as pH controller of secondary water in nuclear power plants. Corrosion Fatigue (CF) tests (R=0.2, 0.1Hz) were conducted to evaluate the effect of acetic acid on the CF crack growth rate in high temperature water at 150°C. Acetic acid significantly influenced the environmental cracking behavior of turbine disc steels in high temperature water. The CF crack growth rates of turbine disc steels increase as the organic acid concentration increase to a critical saturation pH value (~pH 4). Beyond the saturation value of pH, the CF crack growth rates decrease significantly. The higher CF crack growth rate of the higher pH solution in water of intermediate content range (pH 4~pH 5) of acetic acid is due to the higher content of H+ enhancing the reduction reactions. Crack tip blunting prevents the CF cracks from growing with increasing rate in the solution of organic acid concentrations beyond the critical value.

Effect of Constraint Induced by Specimen Geometries on Crack Growth Behavior Under Creep-Fatigue Interaction

2018 ◽  
Author(s):  
Lei Zhao ◽  
Lianyong Xu
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Rates ◽  
Crack Tip ◽  
Crack Growth Behavior ◽  
Growth Behaviour ◽  
Crack Growth Behaviour ◽  
Creep Fatigue ◽  
Crack Growth Rates

Creep-fatigue interaction would accelerate the crack growth behaviour and change the crack growth mode, which is different from that presenting in pure creep or fatigue regimes. In addition, the constraint ahead of crack tip affects the relationship between crack growth rate and fracture mechanics and thus affects the accuracy of the life prediction for high-temperature components containing defects. In this study, to reveal the role of constraint caused by various specimen geometries in the creep-fatigue regime, five different types of cracked specimens (including C-ring in tension CST, compact tension CT, single notch tension SENT, single notch bend SENB, middle tension MT) were employed. The crack growth and damage evolution behaviours were simulated using finite element method based on a non-linear creep-fatigue interaction damage model considering creep damage, fatigue damage and interaction damage. The expression of (Ct)avg for different specimen geometries were given. Then, the variation of crack growth behaviour with various specimen geometries under creep-fatigue conditions were analysed. CT and CST showed the highest crack growth rates, which were ten times as the lowest crack growth rates in MT. This revealed that distinctions in specimen geometry influenced the in-plane constraint level ahead of crack tip. Furthermore, a load-independent constraint parameter Q* was introduced to correlate the crack growth rate. The sequence of crack growth rate at a given value of (Ct)avg was same to the reduction of Q*, which shown a linear relation in log-log curve.

Fatigue Crack Growth Behavior of Titanium Alloy Ti-6Al-4V and Weldment

2001 ◽  
Vol 123 (3) ◽  
pp. 141-146 ◽  
Author(s):  
Mamdouh M. Salama
Keyword(s):  
Growth Rate ◽  
Titanium Alloy ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Titanium Alloys ◽  
Crack Growth ◽  
Growth Rates ◽  
Offshore Structures ◽  
Crack Growth Rates

Optimization of weight, cost, and performance of deepwater offshore structures demands the increased utilization of high strength, light weight, and corrosion resistant materials such as titanium alloys. Titanium alloy Ti-6Al-4V has been considered for several critical components such as risers and taper joints. Because of the novelty of use of titanium alloys in the offshore industry, there is currently no standard governing design of titanium components for offshore structures. Since these structural components are subjected to a complex spectrum of environmental loading, assessment of defect tolerance using fatigue crack growth analysis is generally considered an important design parameter. In this paper, more than 60 crack growth data sets from 20 independent laboratories were collected and analyzed to develop crack growth rate equations for use in defect assessment. These data include the results of fatigue testing of both base material and welded joints in air and seawater with and without cathodic protection and at different R-ratios and test frequencies. The results suggest that for crack growth rates above 10−7 in./cycle, crack growth of Ti-6Al-4V appears to be independent of testing condition and materials processing. At the low crack growth rate (below 10−7 in./cycle), the review revealed that data are very limited. These limited data, however, suggest that the crack growth threshold is dependent on the R-ratio and slightly dependent on material processing. Comparison between crack growth rates of steel and titanium alloy (Ti-6Al-4V) showed that the two materials have very similar behavior.

Fatigue Crack Growth in Type 316 Stainless Steel at High Temperature

1971 ◽  
Vol 93 (4) ◽  
pp. 976-980 ◽  
Author(s):  
P. Shahinian ◽  
H. H. Smith ◽  
H. E. Watson
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
316 Stainless Steel ◽  
Arrhenius Relation ◽  
Crack Growth Rates

The dependence of fatigue crack growth rates on range of stress intensity factor (ΔK) in Type 316 stainless steel was investigated over the temperature range of 75 to 1100 deg F. The data for the most part could be described by a power law relationship. An increase in temperature generally increased crack growth rate for a given ΔK and decreased fatigue life. The dependence of crack growth rate on temperature is not described adequately by an Arrhenius relation over the range investigated. On the other hand, by normalizing ΔK with respect to Young’s modulus, E, the crack growth rates for the various temperatures tend to fall within a single band.

Experimental Study on Fatigue Crack Growth and Residual Strength of Steel 30CrMnSiNi2A under Mixed Corrosive Environments

2008 ◽  
Vol 33-37 ◽  
pp. 261-266
Author(s):  
Sheng Nan Wang ◽  
Yi Li ◽  
Jian Bo Qin ◽  
Ya Long Liu ◽  
Yue Quan Zhou
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Residual Strength ◽  
Growth Rates ◽  
Critical Crack Length ◽  
Corrosive Environments ◽  
Crack Growth Rates

The effects of five single and three mixed corrosive environments on the fatigue crack growth and residual strength of steel 30CrMnSiNi2A were experimentally studied. The crack growth rates in corrosive environments, obtained by using Paris equation, were compared with crack growth rate in lab air. The results showed that the interactions of aggressive environments with fatigue loads caused the accelerations of fatigue crack growth rates in steel 30CrMnSiNi2A. But the effects of various environments on the fatigue crack growth rate are different. Among the environments the most detrimental one was oil-box zone, followed by cookroom&washroom, tank seeper, 3.5%NaCl, moist air, high altitude and dried air. Also, the test data showed the less effect of various corrosive environments on critical crack length, that is, no direct infection of corrosive environments on residual strength capability dominated by fracture toughness.

scholarly journals Orientation Dependence of Hydrogen Accelerated Fatigue Crack Growth Rates in Pipeline Steels

2018 ◽  
Author(s):  
Eun Ju Song ◽  
Joseph A. Ronevich
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Growth Rates ◽  
Orientation Dependence ◽  
Gaseous Hydrogen ◽  
Crack Growth Rates

One of the most efficient methods for supplying gaseous hydrogen long distances is by using steel pipelines. However, steel pipelines exhibit accelerated fatigue crack growth rates in gaseous hydrogen relative to air. Despite conventional expectations that higher strength steels would be more susceptible to hydrogen embrittlement, recent testing on a variety of pipeline steel grades has shown a notable independence between strength and hydrogen assisted fatigue crack growth rate. It is thought that microstructure may play a more defining role than strength in determining the hydrogen susceptibility. Among the many factors that could affect hydrogen accelerated fatigue crack growth rates, this study was conducted with an emphasis on orientation dependence. The orientation dependence of toughness in hot rolled steels is a well-researched area; however, few studies have been conducted to reveal the relationship between fatigue crack growth rate in hydrogen and orientation. In this work, fatigue crack growth rates were measured in hydrogen for high strength steel pipeline with different orientations. A significant reduction in fatigue crack growth rates were measured when cracks propagated perpendicular to the rolling direction. A detailed microstructural investigation was performed, in an effort to understand the orientation dependence of fatigue crack growth rate performance of pipeline steels in hydrogen environments.

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