Corrosion Fatigue Crack Growth Rate Research Articles

Review on Environmentally Assisted Static and Fatigue Cracking of Al-Mg-Si-(Cu) Alloys

This paper reviews the relevant literature and covers the main aspects of the environmentally assisted cracking of Al-Mg-Si-(Cu) alloys. Apart from a brief overview of the major microstructural and mechanical properties, it presents research results on the corrosion sensitivity and stress corrosion susceptibility of Al-Mg-Si alloys. Possible mechanisms of stress corrosion cracking and corrosion fatigue in aluminum alloys, such as anodic dissolution and/or interaction with hydrogen, are considered. A number of factors, including atmospheric or solution conditions, applied stress, and material properties, can affect these mechanisms, leading to environmentally assisted cracking. Specific attention is given to Al-Mg-Si alloys with copper, which may increase the sensitivity to intergranular corrosion. The susceptibility to both intergranular corrosion and stress corrosion cracking of Cu-containing Al-Mg-Si alloys is mostly associated with a very thin layer (segregation) of Cu on the grain boundaries. However, the effect of Cu on the corrosion fatigue and fatigue crack growth rate of Al-Mg-Si alloys has received limited attention in the literature. At the current state of the research, it has not yet been holistically assessed, although a few studies have shown that a certain content of copper can improve the resistance of aluminum alloys to the environment with regard to corrosion fatigue. Furthermore, considerations of the synergistic actions of various factors remain essential for further studying environmentally assisted cracking phenomena in aluminum alloys.

Application of Machine Learning (ML)-based multi-classifications to identify corrosion fatigue cracking phenomena in Naval steel weldments

Corrosion fatigue (CF) crack detection in welded ship hull structures is quite crucial as well as challenging for ensuring their structural integrity. This is conventionally done by offline ship hull survey and inspection methods, which have large time and cost implications. Data-driven approaches of ship hull crack detection are promising in this regard. Corrosion fatigue crack growth rate (CFCGR) behaviour of shipbuilding steel was studied for its base metal (BM), fatigue-prone heat affected zones (HAZs) of Submerged Arc Welding (SAW), and shielded metal arc welding (SMAW) joints of Naval-grade steel. The results indicated the highest CFCGR for BM, intermediate for SAW, and smallest for SMAW welds. This was attributed to 44% lath martensite observed in the SMAW HAZ microstructure as compared to 33% in SAW HAZ. A novel ML-based method has been proposed for CF crack location identification by a multi-classification approach using CFCGR data for structural health monitoring (SHM) applications. Prediction of crack location (either BM, SMAW HAZ, or SAW HAZ) was investigated using K-nearest neighbour (KNN), linear support vector machine classifier (LSVC), Naïve Bayes (NB), decision tree (DT), random forest (RF), and artificial neural network (ANN) models. DT and RF models were found to perform very well even without scaling and hyper-parameter tuning operations and exhibited 98–99% classification accuracy. Scaling and tuning operations resulted in significant improvements in accuracy of KNN models from 43% to 84% (minmax scaling) and 98% (standard scaling). Significant improvement in the accuracy from 37% to 98% ANN model was achieved by standard scaling. The proposed method shall be useful in data-driven real-time crack location identification in ship hull structures.

Effect of different loading conditions on corrosion fatigue crack growth rate of a nickel-based alloy in supercritical water

Advanced ultra-supercritical (A-USC) technology improves the initial steam temperature to 650 °C and more. In such an extremely corrosive medium environment, metallic materials are susceptible to corrosion fatigue. In the present study, the aim is to evaluate the effect of maximum stress intensity factor (Kmax), stress ratio (R), waveform, frequency, and holding time (th) on the corrosion fatigue cracking behavior of C-HRA-2 (a candidate nickel-based alloy for A-USC units) in supercritical water (650 °C/25 MPa). The results show that with the increase of Kmax, the corrosion fatigue crack growth rate (CFCGR) increases and satisfies the exponential relationship. The decrease in R and frequency both cause the rise of CFCGR, which satisfies the logarithmic linear relationship. Sinusoidal and triangular wave loading have no significant effect on the CFCGR. Trapezoidal wave with th has a larger CFCGR while with the rise in th, the CFCGR increases. The crack propagation path is straight, perpendicular to the loading direction, and secondary cracks are also observed. Transgranular and intergranular mixed fractures occurred during continuous loading. The proportion of intergranular fracture increases significantly as holding time is applied. The corrosion fatigue crack growth of C-HRA-2 in supercritical water can be explained by dynamic embrittlement mechanism.

Corrosion fatigue crack growth behavior of a structurally gradient steel for high-speed railway axles

Considering the complex service environments that high speed railway axles are subjected to, the fatigue crack growth (FCG) behavior of a structurally gradient axle steel with different pre-crack depths both in air and a corrosive medium was investigated at a frequency of 5 Hz. The results indicated that in the high ΔK region, the FCG rate was dramatically accelerated by corrosion but the gap narrows as ΔK decreased. The accelerated corrosion FCG rate was a comprehensive result of the acceleration effect of the anodic dissolution, hydrogen-enhanced localized plasticity and the retardation effect of corrosion-induced crack-tip blunting. Despite the fact that the corrosion resistance gradually decreased as the pre-crack depth increased, the FCG rate in the corrosive medium gradually decreased. This was because fatigue loading played a more important role than corrosion in accelerating the corrosion FCG rate.

The Effect of Fatigue Damage on the Corrosion Fatigue Crack Growth Mechanism in A7N01P-T4 Aluminum Alloy

A7N01P-T4 aluminum alloy plates for high-speed trains will experience a certain amount of fatigue damage under alternating loads. Three groups of samples, P0 (no fatigue damage), P1 (loading stress 30 MPa), and P2 (loading stress 70 MPa), were created, and corrosion fatigue crack growth (CFCG) tests were conducted in 3.5 wt.% NaC1 solution. The crack growth rate was found to increase after fatigue damage as the damage degree increased. In addition, the A7N01P-T4 aluminum alloy base metal exhibited obvious secondary cracks and crack bifurcations after fatigue damage. It is believed that fatigue damage causes stress concentration in the material, while a certain degree of stress corrosion cracking occurs during the CFCG growth process. This is because hydrogen (H) easily accumulates and diffuses along the grain boundary, which reduces the strength of the grain boundary, thereby becoming the preferred orientation for crack growth. This explains why the CFCG rate of the material is accelerated following fatigue damage to a certain extent.

Study on corrosion fatigue behavior of heavy piece Ti6Al4V titanium EBW joint in artificial seawater

Titanium alloy has been more and more used in the ocean engineering field. Since the crucial service environment, the corrosion fatigue behavior of the Ti6Al4V alloy EBW joint has been investigated and analyzed. The results show that the grain size of the molten zone decreases gradually from the central line to the base metal symmetrically and the acicular α’ martensite and β phase grain boundaries are the dominating phases of the seam zone. Moreover, the corrosion fatigue crack growth rate of the seam zone was insensitive to the texture of the base metal and crystal orientation of the ti6al4v alloy. It could also be seen that the base metal and the seam zone have different crack growth mechanisms, which is mainly during to the existence of the acicular α‘ martensite in the seam zone and the trend of crack tip energy release. The crack propagation rate of the seam is lower than that of the base metal.

Development of a new approach for corrosion-fatigue analysis of offshore steel structures

Corrosion-fatigue is known to be the dominant failure mechanism in offshore structures, such as offshore wind turbines, due to the constant exertion of cyclic loads in highly corrosive environments. In the present study, the existing corrosion-fatigue crack growth (CFCG) theories and models have been firstly reviewed and discussed, and subsequently a new approach has been proposed to accurately describe the corrosion-fatigue behaviour under various loading conditions and frequencies. To examine the validity of the proposed approach, fatigue crack growth experiments were conducted on S355G10+M medium strength steel compact tension, C(T), specimens at different load levels and frequencies. The experimental data were initially analysed using the traditional fracture mechanics parameter ΔK which was shown to have limitations at elucidating the effects of frequency on CFCG rates in the range of 0.2–0.5 Hz. Therefore, a new fracture mechanics parameter was developed that allows these effects to be seen and accounted for more clearly. Furthermore, a new CFCG model was developed, using the introduced fracture mechanics parameter, for predicting the crack growth rates in seawater from the short-term test data in air. The proposed model has been found to correlate well with experimental data from corrosion-fatigue experiments on S355G10+M from this study and S355J2+N structural steel data available in the literature.

Effect of Microstructure on the Corrosion Fatigue Crack Growth of Low and Medium Steels

This article studies the effect of microstructure on the corrosion fatigue crack growth behavior of low and medium carbon steels. 45 steel and 15CrMo were selected and five typical microstructures were obtained by different heat treatment processes. The microstructures of 45 steel and 15CrMo after annealing and normalizing are both ferrite and pearlite, but the proportions of ferrite and pearlite in the four microstructures are different. The quenching and tempering microstructure of 45 steel is tempered fine pearlite. Corrosion fatigue tests were conducted on specimens with different microstructures of the two materials. Expressions of corrosion fatigue crack growth rate and da/dN∼ΔK fitting curves of different microstructures were obtained. Comparison of da/dN∼ΔK curves of 45 steel shows that tempered fine pearlite has the best resistance to corrosion fatigue crack growth, and the content of pearlite has a great impact on the corrosion fatigue crack growth behavior for specimens with the microstructure of ferrite and pearlite. In the low ΔK region, the corrosion factor plays a dominant role in fatigue crack growth, and the corrosion resistance of pearlite is weak, which leads to a higher da/dN in the normalized state. In the high ΔK region, fatigue factor dominants, since the fatigue resistance of pearlite is strong, da/dN of the annealed state is higher. The experimental results of 15CrMo showed the same crack growth rate change regulation as that of 45 steel, which further proves the effect of pearlite on the corrosion fatigue crack propagation behavior.

Fatigue Crack Growth of Z2CND18-12N Austenitic Stainless Steel and Its Heat-Affected Zone in a Dissimilar Metal Weld Joint in 325°C Water

Fatigue crack growth (FCG) in Z2CND18-12N austenitic stainless steel and its heat-affected zone (HAZ) in the Z2CND18-12N/16MND5 dissimilar metal weld joint has been investigated in room temperature air and 325°C water. The dependence of FCG rates on specimen orientation in room temperature air got somewhat evident as ΔK decreased to 13 MPa√m. However, for Z2CND18-12N steel, the influence of specimen orientation on the FCG in room temperature air and the corrosion fatigue crack growth (CFCG) in 325°C water was slight and negligible. A moderate increase in the FCG rate was observed for the Z2CND18-12N HAZ in room temperature air at a low ΔK = 13 MPa√m (near ΔK threshold), compared with its base metal. However, the CFCG rate difference between the Z2CND18-12N HAZ and its base metal was minor. The CFCG in the Z2CND18-12N in 325°C water (without the addition of H2) was consistent with a slip-oxidation-rupture mechanism and the oxide film on the corrosion fatigue crack tip mainly consisted of Fe3O4.

Titanium alloy corrosion fatigue crack growth rates prediction: Peridynamics based numerical approach

This study presents a numerical approach for modelling the Corrosion Fatigue Crack Growth (CFCG) in conventional casting and additively manufactured Ti6Al4V alloys. The proposed numerical model, based on Peridynamics (PD), combines the PD Fatigue Crack Growth (FCG) model and PD diffusion model in order to couple the mechanical and diffusion fields existing in the material due to the impact of environmental fatigue. The mechanical field is responsible for the characterisation of the changes to the structure due to the fatigue loading conditions. The diffusion field is based on the modelling of the adsorbed-hydrogen Stress Corrosion Cracking (SCC), in particular, the Hydrogen Embrittlement (HE) model is considered. The proposed approach has been validated using experimental data available in the literature showing the capability of the tool to predict the CFCG rates.

Corrosion-fatigue crack growth behaviour of wire arc additively manufactured ER100S-1 steel specimens

The wire arc additive manufacturing (WAAM) technology is a promising fabrication technique which has been proven to have many advantages for producing large structures; however, the fatigue and corrosion-fatigue performance of WAAM steel components for application in the marine environments is still unexplored. In this study, the WAAM technique was employed to fabricate four specimens made of ER100S-1 steel, which were then tested under cyclic loading conditions in seawater to assess the corrosion-fatigue crack growth (CFCG) behaviour and hence suitability of this fabrication technology for offshore renewable energy applications. The test duration, cracking mechanisms and CFCG rate were investigated for each specimen and the material’s behaviour was investigated by considering the microstructural examinations. Furthermore, the obtained results were compared with the BS7910 standard recommended trends and experimental data available in the literature for conventionally built weldments made of different grades of steel which are commonly used for offshore applications.

Effect of heat treatment on fatigue crack growth behavior of 316NG austenitic stainless steel in deaerated water at 325 °C

316NG (00Cr17Ni12Mo2N) austenitic stainless steel was heat-treated at 600, 725 and 1000 °C to investigate the effects of heat treatment temperature and holding time on the fatigue crack growth behavior of this steel in deaerated water at 325 °C. It is found that fatigue crack growth rates in air at room temperature are decreased after the heat treatments, due to a reduced dislocation density. Corrosion fatigue crack growth rates in water at 325 °C are also decreased after the heat treatments at 600 and 1000 °C for 1 h, while the heat treatment at 725 °C leads to a moderate increase in the fatigue crack growth rate. The latter phenomenon results from a higher amount of CrNbN (Z-phase) precipitates formed in the steel after the annealing at 725 °C.

Corrosion-Fatigue Crack Growth Performance of Titanium Grade 29 Welds in Tapered Stress Joints

Abstract Design of a steel catenary riser requires the use of connection hardware to decouple the large bending moments induced by the host floater at the hang-off location. Reliability of this connection hardware is essential, particularly in applications involving high pressure and high temperature fluids. One option for this connection hardware is the metallic tapered stress joint. Titanium (Ti) Grade 29 has been identified as an attractive material candidate for demanding stress joint applications due to its “high strength, low weight, superior fatigue performance and innate corrosion resistance”.2 Titanium stress joints for deepwater applications are typically not fabricated as a single piece due to titanium ingot volume limitations, thus making an intermediate girth weld necessary to satisfy length requirements. As with steel, the potential effect of hydrogen embrittlement induced by cathodic and galvanic potentials must be assessed to ensure long-term weld integrity. This paper describes testing from a joint industry project (JIP) conducted to qualify titanium stress joint (TSJ) welds for ultra-deepwater applications under harsh service and environmental conditions. Corrosion-fatigue crack growth rate (CFCGR) results for Ti Grade 29 flat welding-groove weld (1G/PA) gas tungsten arc welding (GTAW) specimens in seawater under cathodic potential and sour brine under galvanic potential are presented and compared to vendor recommended design curves.

Corrosion fatigue crack growth mechanisms in welded joints of marine steel structures

This paper presents a model of fatigue crack growth in a welded joint and a two-dimensional model of anodic dissolution based on Donahue model and anodic dissolution mechanism, respectively. In addition, a model for predicting the corrosion fatigue crack growth rate in welded joints of steel marine structures is established and crack growth mechanisms are analyzed. The results show that during early stages of crack growth, corrosion fatigue crack growth rate in welded joints is mainly controlled by corrosion action, whereas cyclic loading becomes more influential during the later stage of crack propagation. Loading frequency and effective stress ratio can affect rupture period of protective film at the corrosion fatigue crack tip and the length of corrosion crack increment, respectively, which changes the influence of corrosion action on crack growth rate. However, the impact of stress amplitude on crack growth rate is only significant when crack propagation is caused by cyclic loading. Welding residual stress not only improves the effective stress ratio of cyclic loading, but also promotes crack closure and increases corrosion fatigue crack growth rate in welded joints. Compared to corrosion action, welding residual stress has a more significant influence on crack growth caused by cyclic loading.

Corrosion fatigue crack propagation behavior of A7N01P‐T4 aluminum alloy welded joints from high‐speed train underframe after 1.8 million km operation

AbstractUsing the potentiodynamic polarization analysis, the fatigue crack propagation behavior of A7N01P‐T4 aluminum alloy metal inert gas welded joints cut from a high‐speed train underframe after 1.8 million km operation was studied in air and in a 3.5 wt% NaCl solution. The fracture surface and crack growth path were analyzed using optical microscopy, scanning electron microscopy, and electron backscattered diffraction. The results reveal that the corrosion fatigue crack growth rate of an A7N01P‐T4 welded joint in a 3.5 wt% NaCl solution is higher than that in air. Furthermore, the corrosion fatigue crack growth rate is noted to be the fastest in the heat‐affected zone, followed by the base metal, whereas it is the slowest in the weld metal, which is consistent with the corrosion resistance of the A7N01P‐T4 joints. The second phase is observed to exhibit a significant influence on the corrosion fatigue crack propagation path. The cracks are noted to grow toward the soft orientation and have obvious plastic deformation during the propagation process, which indicates that the anodic dissolution is the main cause of the corrosion fatigue crack growth.

Crack growth direction effects on corrosion-fatigue behaviour of offshore wind turbine steel weldments

In this study corrosion-fatigue tests have been conducted on fracture mechanics specimens extracted from an S355 G10+M structural steel welded plate. The tests have been performed on compact tension specimens with the crack tip located in the heat affected zone. The corrosion-fatigue test results from this study have been compared with the data available on the base metal as well as air tests on the same material. Moreover, the obtained results have been compared with the corrosion-fatigue data available in the literature on a wide range of steels and also the fatigue trends for welded joints in free-corrosion condition recommended in the BS7910 Standard. The effect of the specimen orientation, with respect to the weld region, is also examined in this study and it has been found that higher corrosion-fatigue crack growth rates are generally observed in the tests with 0° orientation. The results have also shown that the corrosive environment has significant effects on the fatigue crack growth acceleration at the beginning of the tests; however, as the crack propagates, the environmental damage effect on crack growth behaviour becomes less pronounced. The results presented in this study are discussed in terms of improvement in the structural integrity assessment of offshore wind turbine monopiles.

Laser shock peening-induced surface gradient stress distribution and extension mechanism in corrosion fatigue life of AISI 420 stainless steel

Surface gradient stress distribution was prepared on AISI 420 martensitic stainless steel (MSS) by massive laser shock peening treatment (MLSPT) with different pulse energies, and effects of MLSPT on residual stress and corrosion fatigue properties in NaCl solutions with different pH values were investigated by microstructural observation, residual stress measurement, corrosion fatigue test, and fractural morphology. Results showed that the coupling effect of MLSPT-induced surface microstructural evolution and gradient stress distribution effectively contributed to an extension in corrosion fatigue properties. Furthermore, the corrosion fatigue crack growth rate equation considering both gradient compressive residual stress and pH value was developed.

Bayesian model updating for the corrosion fatigue crack growth rate of Ni-base alloy X-750

Nickel base Alloy X-750, which is used as fastener parts in light-water reactor (LWR), has experienced many failures by environmentally assisted cracking (EAC). In order to improve the reliability of passive components for nuclear power plants (NPP's), it is necessary to study the failure mechanism and to predict crack growth behavior by developing a probabilistic failure model.In this study, The Bayesian inference was employed to reduce the uncertainties contained in EAC modeling parameters that have been established from experiments with Alloy X-750. Corrosion fatigue crack growth rate model (FCGR) was developed by fitting into Paris’ Law of measured data from the several fatigue tests conducted either in constant load or constant ΔK mode.These parameters characterizing the corrosion fatigue crack growth behavior of X-750 were successfully updated to reduce the uncertainty in the model by using the Bayesian inference method. It is demonstrated that probabilistic failure models for passive components can be developed by updating a laboratory model with field-inspection data, when crack growth rates (CGRs) are low and multiple inspections can be made prior to the component failure.

Corrosion fatigue crack growth behavior of 316NG heat affected zone in simulated pressurized water reactor environment

The corrosion fatigue crack growth (FCG) behavior of the 316NG heat affected zone (HAZ) exposed to simulated pressurized water reactor (PWR) environment has been investigated. The results show that significant residual strains and lattice misorientations exist in the HAZ near the welding root. Z-phase precipitates are present in both the HAZ and annealed 316NG base metal. The FCG rate of the HAZ is much higher than that of the base metal. In PWR water, the corrosion FCG rate of the HAZ is strongly dependent on the cyclic loading frequency, but the effect of dissolved oxygen is negligible.

Effect of loading frequency on corrosion fatigue crack growth rate of 7N01 aluminum alloy

The fatigue damage of engineering structures is mostly caused by cyclic stress and external environmental factors. Therefore, the study of corrosion fatigue crack propagation is of great significance to the safety and durability of structures. The effects of different loading frequencies (10Hz, 1Hz and 0.1Hz) on fatigue crack growth rate of 7N01 aluminum alloy in humid air were studied by using load control method. The results show that the corrosion fatigue crack growth rate is basically the same at 10Hz and 1Hz, When the loading frequency decreases to 0.1Hz, the corrosion fatigue crack growth rate is slightly higher than 10Hz and 1Hz.