Crack Sensitivity Research Articles

Corrosion Behavior of Tubing in High-Salinity Formation Water Environment Containing H2S/CO2 in Yingzhong Block

To clarify the corrosion behavior of P110SS material under the synergistic action of multiple factors such as a CO2/H2S coexistence environment, a high temperature, and high-salinity formation water, a series of simulation tests and analyses were carried out in this paper. High-temperature high-pressure autoclaves, scanning electron microscopy, and a three-dimensional microscope were used to analyze and evaluate the changing trend of the corrosion performance of P110SS tubing material under different temperatures and a H2S/CO2 partial pressure ratio in a high-salinity formation water environment, and the corrosion cracking sensitivity and pitting sensitivity of the material with stress were compared and analyzed. The results indicate that the average corrosion rate of P110SS material without stress increases with the rising test temperature, and the corrosion damage worsens with an increase in the H2S: CO2 partial pressure ratio. The highest corrosion rate for P110SS material is 0.99 mm/a. When the test temperature varies from 80 °C to 180 °C and PH2S:PCO2 = 0.53:0.17, the P110SS material with a loading stress of 85% YSmin is not susceptible to stress corrosion cracking (SCC). Although surface pitting nucleation is evident at a high temperature of 180 °C, no expansion-induced cracking or fracture phenomena occur.

Investigation of hot cracking susceptibility in welding of AA5052 aluminium alloy

ABSTRACTThe present research work focuses on the investigation of hot cracking susceptibility of TIG-welded AA5052 aluminum alloy with two filler materials ER4043 and ER5356, respectively. Welded samples were undergone Houldcroft testing to estimate the solidification cracking susceptibility in the weldment. Microstructural characterization, microhardness testing, X-ray diffraction analysis and scanning electron microscope examination were performed on the weldments. The solidification cracking is not identified while using ER4043 since it has relatively narrow freezing range. High crack sensitivity of 29% is found when welding was performed using ER5356. Hardness for the specimens welded with ER4043 filler material showed 106 ± 3 HV and 116 ± 2 HV in heat affected zone (HAZ) and fusion zone (FZ), respectively, but the specimens welded with ER5356 filler material showed higher hardness of 160 ± 2 HV and 150 ± 4 HV in HAZ and FZ, respectively. The specimens welded by ER4043 and ER5356 showed the formation of Mg2Si at FZ.

Corrigendum to “Prediction on cold crack sensitivity using hydrogen embrittlement index measured from in situ slow-strain-rate testing for multipass flux-cored arc weld metals of shipbuilding and offshore steels” [Materials Characterization 197 (2023) 112637

Corrigendum to “Prediction on cold crack sensitivity using hydrogen embrittlement index measured from in situ slow-strain-rate testing for multipass flux-cored arc weld metals of shipbuilding and offshore steels” [Materials Characterization 197 (2023) 112637

Effect of MgF2 coating on stress corrosion cracking behavior of Mg−Zn−Ca alloy in simulated body fluid

The stress corrosion cracking behavior of Mg−3wt.%Zn−0.2wt.%Ca (MZC) alloy and fluoride (MgF2) coated Mg−3wt.%Zn−0.2wt.%Ca alloy (MZC-MF) for bone implant applications was investigated using slow strain- rate tensile (SSRT) tests in simulated body fluid (SBF). The results show that MgF2 coating could significantly improve the corrosion resistance and prolonged fracture failure time of MZC alloy. MgF2 coating also greatly reduced the stress corrosion cracking sensitivity of MZC alloy in SBF. Compared to MZC alloy, stress corrosion cracking sensitivity index (Iscc) of MZC-MF alloy decreased by 21% (ultimate tensile strength, UTS), 22% (time to failure, tf), 23% (elongation after fracture, δ), 7% (reduction ratio of cross-sectional area after fracture, ϕ) and 15% (inner product work, A), respectively.

Numerical investigation into effects of fracture behavior on edge cracking sensitivity

Numerical investigation into effects of fracture behavior on edge cracking sensitivity

Predicting solidification cracking in directed energy deposition of Hastelloy X alloys based on thermal-mechanical model

Directed energy deposition (DED) has received extensive attention in recent years owing to its advantages of near-net forming and high design freedom. However, the thermal stress induced by rapid heating and cooling during fabrication of DEDed Hastelloy X (HX) alloys usually results in solidification cracking. To suppress or even eliminate solidification cracking by optimizing processing parameters, it is necessary to establish a correlation between stress in the last stage of solidification and solidification cracking sensitivity (SCS) of DEDed HX alloys. In this study, we first confirmed the critical role of stress in solidification cracking by comparing the simulation results calculated by a thermal-mechanical model with an experimental crack distribution and then proposed a stress-related index for describing the SCS. By calculating the index in different deposited regions and with different processing parameters, we successfully predicted the crack-prone regions at the part scale and the relationship between processing parameters and SCS. The results show that there are almost no cracks in the edge region of the DEDed HX alloy sample, while cracks are mainly generated in the region within a quarter of the width from the edge of the DEDed HX alloy sample. Moreover, solidification cracking can be effectively suppressed under a high heat input. All these simulated results are in good agreement with the experimental results. These findings are of significance to understand the solidification cracking mechanism in DED, which can be used to guide the fabrication of DED crack-free HX alloys.

Influence of residual stress on the cracking of the laser-cladded high-hardness coating

A high-hardness Fe-C-W-Nb-B coating was prepared on 42CrMo substrate by laser cladding. The crack sensitivity, microstructure, and residual stress were studied and compared with commercial Fe-C-W-Mo coating produced by Höganas. The results exhibit that all coatings had microstructure consisting of a martensite matrix and reinforcements. The single-pass coating had a residual stress of about −695.8 MPa, 1.21 times that of the commercial coating (-575.6 MPa). The coating exhibited compressive residual stress due to thermal and transformation stress interaction. The multi-pass coating was crack-free and presented a hardness higher than 900 HV. However, the commercial coating cracked, despite its hardness being only 791.4 HV. The high-hardness coating had a more uniform distribution of residual stress than the commercial coating, reducing the cracking risk.

Effect of additive manufacturing and subsequent heat and/or surface treatment on the hydrogen embrittlement sensitivity of 316L austenitic stainless steel

Austenitic stainless steels (ASS) offer attractive characteristics for use in hydrogen service, such as low hydrogen diffusivity and high solubility. The role of the production process is, however, still unclear. Especially the effect of additive manufacturing (AM) on the hydrogen interaction is not extensively researched yet. The present work compares the hydrogen embrittlement sensitivity of conventional (cold rolled and annealed) and additive manufactured 316L ASS and evaluates the possible advantage of performing a heat treatment and/or reducing the surface roughness post printing. AM increases the hydrogen solubility but the hydrogen diffusivity was only slightly reduced. The heat treatment reduced the hydrogen solubility of the AM materials and significantly increased the hydrogen diffusivity. Despite these observations, the conventional 316L ASS shows a higher hydrogen embrittlement (HE) sensitivity compared to AM316L. This is linked to the increased hydrogen-assisted cracking sensitivity of conventional 316L ASS. The heat treated microstructure behaves similarly as the as-built material in terms of HE sensitivity, while a major improvement is observed when the surface oxide layer formed during the heat treatment is maintained since this reduces hydrogen absorption. Surface polishing intensifies the HE sensitivity which is linked to a higher surface hydrogen concentration leading to more crack initiation.

Effect of pre-strain on edge formability of high strength steels for chassis applications

There is a high level of uncertainty in the prediction of edge cracking during the design and manufacturing of high strength sheet metal products. Edge ductility is a complex parameter to measure since it is not an intrinsic property of the material, but it also depends on the trimming strategy/parameters that have been applied to the edge (edge preparation method, cutting/punching clearance, etc.). Furthermore, most forming processes involve more than one operation where the material can be deformed in a first stage, then trimmed or punched and further deformed in a final forming step to obtain the desired shape. Therefore, in order to design a robust and safe forming process able to predict the risk of edge cracking, it is crucial to understand the influence of pre-strain on the residual formability of trimmed edges. This paper analyses the effect of different pre-strain levels and paths (uniaxial tension, plane strain and equi-biaxial stretching) on the sheared edge ductility of a Complex Phase (CP) steel and a high strength low alloy (HSLA) steel used for automobile chassis applications. To this purpose, rectangular specimens are cut out from pre-strained samples and punched. Hole Tension Tests (HTTs) in combination with Digital Image Correlation (DIC) are carried out to determine the edge fracture strain of undeformed and pre-strained samples. The results are discussed in terms of major strains obtained from DIC. The proposed methodology allows describing the edge cracking sensitivity of high-strength steel sheets as a function of the pre-deformation state and can be useful to predict the risk of edge cracking more accurately in forming simulations.

Implementation of the Bigot Method for the Determination of Drying Sensitivity and Removal of Cracks in Roof Tile Production

Türkiye’de kiremit sektörü her geçen gün gelişmekte ve geleneksel üretimlerin yerini ar-ge çalışmalarıyla değerlendirilen süreçler almaktadır. Bu doğrultuda Ece Kiremit üretim tesislerinde kiremit ürünlerin şekillendirme sonrası doğal kurutma esnasında kuruma çatlaklarının tespiti ve giderilmesi için bigot ve yeni reçete çalışmaları yapılmıştır. Bu hataların giderilebilmesi için tüm hammaddelerin Bigot Eğrilerinin çıkarılması, karakterizasyonları ve yeni reçete çalışmaları gerçekleştirilmiştir. Bigot Eğrisi mantığına göre kiremit numunelerinin nem atma özellikleri ve kuruma küçülmelerinin tespiti için tüm örneklerin 100 ºC’de kuruma eğrileri çıkarılmış ve Bigot’a göre küçülme – nem eğrileri verilmiştir. Yapılan deneysel çalışmalar sonucunda, çalışmada yer alan Gülücek kil, Gülücek kist ve Kınık kisti olmak üzere üç farklı kil çalışılmıştır. Gülücek Kistinin kuru küçülmesinin diğer hammaddelere göre daha az olduğu, neminin az bir kısmını (%1,04) attığında bütün kuru küçülmesini bitirdiğinden dolayı reçete içerisinde yüksek miktarda kullanımının kuruma çatlaklarına sebep olacağı çözümlenmiştir. Ayrıca yapılan karakterizasyon analizlerinin sonuçlarından da anlaşılabileceği gibi, klorit ve klinoklor minerallerini içeren bir yapıda olduğundan su tutma özelliğinin de diğer hammaddelerden daha fazla olduğu görülmüştür. Oluşturulan reçete çalışmalarında 4 farklı reçete yapılarak Gülücek Kistinin oranı reçete içerisinde düşürülmüştür. Yapılan 4 reçetede de kuruma küçülmelerinin zamana bağlı olarak daha geniş aralıkta olduğu, fakat içerisindeki nemi daha çabuk bıraktığı görülmektedir. Özellikle Reçete 3 ve 4’ün öncelikli olarak üretim denemelerinin yapılması, olumsuz olabilecek durumlarda reçete 2’nin üretim denemesinin yapılması uygun bulunmuştur.

Fabrication of Fe–30Al alloy using plasma arc welding powered twin-wire directed energy deposition-arc process: Droplet transfer, microstructure, and mechanical property investigation

Intrinsic brittleness and cold cracking sensitivity of Fe–Al intermetallic compounds make their fabrication and processing difficult. In recent years, an innovative additive manufacturing (AM) technology, twin-wire directed energy deposition-arc (TW-DED-arc), has been developed to prepare defect-free Fe–Al alloys via in-situ alloying of Fe and Al elements in a gas tungsten arc welding (GTAW) generated molten pool. However, unconstrained plasma of regular tungsten arc leads to excessive heating area and residual stress during AM buildup. And relatively weak arc pressure of GTAW makes composition inhomogeneity a concern in the in-situ alloying molten pool. To solve the two potential drawbacks, plasma arc welding (PAW) possessing higher energy density and arc pressure is used to power the TW-DED-arc process and fabricate Fe–30Al alloy. In the present research, a special wire-feeding strategy for stable twin-wire feeding of Fe and Al wires is successfully developed to overcome the droplet transfer difficulty induced by constrained arc of PAW and large thermophysical properties difference of heterogeneous filler wires. And according to microscopy characterization results, the innovative PAW powered TW-DED-arc process is capable of fabricating defect-free Fe–30Al bulk sample with homogeneous Al content and epitaxial columnar grain structures. The successful application of PAW-powered TW-DED-arc technique in fabrication of iron aluminide provides stabler and more efficient route for iron aluminide component.

A new test for evaluating crack sensitivity of materials during welding

A new test for evaluating crack sensitivity of materials during welding

Improving the strength and SCC resistance of an Al-5Mg-3Zn alloy with low-angle grain boundary structure

The strength of traditional Al-Mg alloys is relatively low because it mainly relies on solid solution strengthening. Adding a third component to form precipitation can improve their strength, but it usually leads to high-stress corrosion cracking (SCC) sensitivity due to the formation of high-density precipitates at grain boundaries (GBs). So far, it is still challenging to improve the strength of Al-Mg alloys without reducing SCC resistance. Herein, a nanostructured Al-5Mg-3 Zn alloy with a good yield strength of 336 MPa and good elongation was successfully produced. By dynamic plastic deformation and appropriate annealing treatment, near-equiaxed nanograins were introduced in the nanostructured Al-5Mg-3 Zn alloy with a high proportion (71%) of the low-angle grain boundary. TEM statistical investigations show that the precipitation of active T' phase at GBs has been greatly suppressed in the nanostructured Al-5Mg-3 Zn alloy at sensitized conditions, and the area fraction of GB precipitates is reduced from 72% to 21%, which significantly decreases the SCC susceptibility. This study provides guidance for developing advanced Al-Mg alloy with high SCC resistance.

Effect of LaB6 doping on the microstructure, microhardness and corrosion behavior of laser cladded FeCoNiCrMo coating on Ti6Al4V

In order to improve the microhardness and corrosion resistance of Ti6Al4V alloy, LaB6 powders was added to the FeCoNiCrMo high entropy alloy coatings fabricated by laser cladding on Ti6Al4V. The microstructure, corrosion resistance and microhardness of LaB6/HEA coatings were analyzed by SEM, EDS, XRD, TEM and performance characterization equipment. The results showed that the appropriate content of LaB6 (2 wt%) could significantly reduce the cracking sensitivity of the coating, and in-situ synthesized La2O3 refined the microstructure and achieve fine grain strengthening. The reduction of cracks and refinement of the microstructure improved the corrosion resistance of HEA. At the LaB6 content of 2 wt%, the corrosion current density of the coating was 2.164 × 10−6 A·cm−2, passive potential was 1.339 V, and the number and size of pitting on the surface of the sample were the lowest, indicating that the passivation film had the strongest resistance to corrosive media. In addition, at the amount of LaB6 addition of 2 wt%, the microhardness of the coating could reach up to 987 HV0.3, which could be attributed to the in-situ synthesis of the ceramic phase TiBX and the refinement of the grains.

Study on crack healing performance of Al2O3/SiCw/TiSi2 new ceramic tool material

In consideration of the crack sensitivity in ceramics, a new alumina-based ceramic material with excellent crack healing ability was successfully fabricated by adding SiC whiskers and TiSi2 particles. Different sizes of cracks were prefabricated on the surface of the material with the diamond indenter, and corresponding crack healing behavior was studied by high temperature oxidation experiments in a muffle furnace under air. The influences of healing temperature, healing time, and crack size on the surface morphology and flexural strength of the material were investigated in detail. When the crack width was 0.68 μm, the appropriate temperature and duration time for crack healing and full-strength recovery were 800 °C for 60 min or 1000 °C for 30 min, respectively. The maximum crack size capable for self-healing of the ceramic material was 2c = 250–300 μm and w = 0.68 μm, and the corresponding healing condition was of 800 °C/60 min. The crack healing of Al2O3/SiCw/TiSi2 ceramics was primarily driven by the high temperature oxidation reactions of Ti5Si3 and SiCw. Ti5Si3 was a new phase formed during sintering, and its formation could be described by thermodynamically feasible reactions. The new crack healing mechanism was revealed deeply, including both the local crack bridging generated by the in-situ development of TiO2 and the liquid phase filling of SiO2 intermediate oxides (Si2O3 and SiO). This research conclusion has great significance for the repairing and remanufacturing of ceramic materials with crack defects.

Stress corrosion cracking of X80 steel heat-affected zone in a near-neutral pH solution containing Bacillus cereus

Bacillus cereus (B. cereus) is observed to have varying effects on the stress corrosion cracking (SCC) sensitivity of different microstructures in the simulated heat-affected zone (HAZ) of X80 steel. At open circuit potential (OCP), the SCC sensitivity of different microstructures increased from 3.40–7.49% in an abiotic medium to 10.22–15.17% in a biotic medium. At −0.9 V (SCE), it increased from 22.81–26.51% to 35.76–39.60%. The increment in SCC sensitivity upon exposure to B. cereus was highest in the coarse-grained HAZ (7.68 and 16.79% at OCP and −0.9 V, respectively), followed by the intercritical and fine-grained HAZs. Owing to differences in the phase composition, grain boundary type, dislocation density, and surface volta potential, the initial adhesion number and position of B. cereus in the microstructure of the HAZ were differed, resulting in different sensitivities to SCC.

An FFT-based crystal plasticity phase-field model for micromechanical fatigue cracking based on the stored energy density

A novel FFT-based phase-field fracture framework for modelling fatigue crack initiation and propagation at the microscale is presented. A damage driving force is defined based on the stored energy and dislocation density, relating phase-field fracture with microstructural fatigue damage. The formulation is numerically implemented using FFT methods to enable modelling of sufficiently large, representative 3D microstructural regions. The early stages of fatigue cracking are simulated, predicting crack paths, growth rates and sensitivity to relevant microstructural features. Crack propagation through crystallographic planes is shown in single crystals, while the analysis of polycrystalline solids reveals transgranular crack initiation and crystallographic crack growth.

Effect of concrete mixing plant sludge powder on properties of ultra-high performance concrete

The output of concrete mixing plant sludge (CMPS) is large and increases year by year, which needs to be disposed urgently. The effect of CMPS powder replacing silica fume (SF) on the properties of ultra-high performance concrete (UHPC) was investigated through testing the fluidity, compressive strengths, shrinkage, pore structure, micromorphology and nanoscale properties. The obtained results indicated that the use of CMPS powder substituting SF improved the fluidity of UHPC; 20% CMPS powder replacing SF increased the compressive strengths of UHPC, but with the further increase of CMPS powder, the strengths of UHPC were reduced, and the compressive strength of UHPC including 60% CMPS powder was less than 100 MPa at 28 days; the incorporation of CMPS powder increased the shrinkage of UHPC, so it is necessary to pay attention to the cracking sensitivity of CMPS powder UHPC; the use of CMPS powder replacing 20% SF produced more calcium silicate hydrate and reduced porosity of UHPC, and had no remarkable effect on the interfacial transition zone of UHPC.

Microstructure and Fatigue Behavior of High-Performance Aluminum Alloy Al2024 Produced by Laser Powder Bed Fusion

Aluminum-based alloys are widely used in high-performance structural applications. Therefore, the opportunity to fabricate aluminum components using Laser Powder Bed Fusion (L-PBF) is a matter of great interest. In particular, the Al2024 alloy is extensively used for conventional part production but its processability by L-PBF remains a challenge because of its hot cracking sensitivity upon solidification. The new Reactive Additive Manufacturing (RAM) technology by Elementum 3D enables the production of innovative powders characterized by metal matrix and nanoceramic particles that can be processed using L-PBF. The ceramic nanoparticles of 2 % by weight improves properties and prevents Al2024-RAM2 alloy cracking during solidification. The present study investigates the fatigue performance of Al2024-RAM2 alloy manufactured by L-PBF using an SLM 280 HL equipment with a nominal layer thickness of 60 µm. A set of miniature vertical fatigue specimens were manufactured then underwent to a heat treatment T6. The specimens were tested in the as-built state (i.e., without any surface post-processing) under cyclic plane bending at a load ratio R = 0 at a frequency of 25 Hz. The fatigue performance was determined and compared to that of another Al-alloy produced by L-PBF. Specimens were examined by using optical microscopy and SEM analysis to determine the microstructure. The fracture surfaces of vertical specimens were investigated in the SEM to determine the mechanisms of crack initiation.

Mechanical performance of asphalt base layers with high RAP content and recycling agents

With circularity in mind, adding reclaimed asphalt in new asphalt mixtures is a common practice. While aiming for higher recycling rates, the need for better control of the mixture performance increases. Recycling agents are often proposed to restore the properties of aged binders. This study investigates the mechanical performance of plant-produced hot mix asphalt for base layers with high reclaimed asphalt content and recycling agents. Two field test tracks, each containing a section with and without a recycling agent, were constructed to allow for long-term performance evaluation. Plant-produced asphalt mixture from all sections was sampled and compacted in the laboratory and subjected to various mechanical tests, including rutting, stiffness, fatigue, cracking and water sensitivity. Besides a lower indirect tensile strength, the overall results indicate a limited influence of the used recycling agents on the mechanical performance of the mixtures, particularly in terms of resistance to rutting and fatigue cracking.