High-pressure Environment Research Articles

An in-situ view cell system for investigating swelling behavior of elastomers upon high-pressure hydrogen exposure

The transition to hydrogen as a clean and efficient energy carrier is impeded by challenges in the compatibility of hydrogen with materials used within hydrogen infrastructure. Elastomers, crucial in sealing components, often exhibit premature failures in high-pressure hydrogen environments due to excessive swelling. This study employs an innovative in-situ view cell system to assess the swelling behavior of hydrogenated nitrile butadiene rubber (HNBR) under various hydrogen conditions. The system, designed to withstand pressures up to 96.5 MPa, incorporates Digital Image Correlation (DIC) for strain measurements and volume estimation. Results reveal non-linear volume increases during depressurization, challenging conventional assumptions. Furthermore, investigations into peak hydrogen pressures and pressure-holding scenarios during decompression highlight complex swelling trends. The introduction of a novel computer vision (CV) method enhances precision in volume estimation, overcoming DIC limitations. The study provides insights into mitigating elastomer swelling, crucial for developing robust materials to support future hydrogen-driven energy systems.

PRIORITIZING PATIENT SAFETY BY HEALTHCARE PROFESSIONALS IN EMERGENCY AND URGENT CARE ENVIRONMENTS

Objective: Highlighting the importance of Patient Safety guidelines in Urgency and Emergency care settings in Brazil. Theoretical Framework: Awareness among healthcare professionals of the importance of following patient safety standards is an extremely relevant topic that has recently gained prominence. Thus, adverse events in hospital institutions, often caused by human errors, increasingly highlight the need to rethink the care models used. Method: An integrative literature review was conducted, along with data analysis, in the following stages: pre-analysis, material exploration, data treatment, and inference/interpretation of results. Results and Discussion: In line with the literature from various authors, the need for the implementation of actions aimed at ensuring safe and quality healthcare was evidenced. Implications of the Research: Providing insights into the optimization of patient safety protocols specific to emergency and emergency care settings, aiming to reduce medical errors and improve clinical outcomes. Originality/Value: The value of this research is evidenced by its innovative approach in analyzing patient safety practices in emergency and emergency care services. By investigating the specific challenges faced in these dynamic and high-pressure environments, this research highlights the importance of new perspectives on how to improve patient safety in critical situations.

Effect of Hydrogen Charging on the Mechanical Properties of High-Strength Copper-Base Alloys, Austenitic Stainless Steel AISI 321, Inconel 625 and Ferritic Steel 1.4511

Hydrogen embrittlement (HE) poses the risk of premature failure for many metals, especially high-strength steels. Due to the utilization of hydrogen as an environmentally friendly energy source, efforts are made to improve the resistance to HE at elevated pressures and temperatures. In addition, applications in hydrogen environments might require specific material properties in terms of thermal and electrical conductivity, magnetic properties as well as corrosion resistance. In the present study, three high-strength Cu-base alloys (Alloy 25, PerforMet® and ToughMet® 3) as well as austenitic stainless AISI 321, Ni-base alloy IN 625 and ferritic steel 1.4511 are charged in pressurized hydrogen and subsequently tested by means of Slow Strain Rate Testing (SSRT). The results show that high-strength Cu-base alloys exhibit a great resistance to HE and could prove to be suitable for materials for a variety of hydrogen applications with rough conditions such as high pressure, elevated temperature and corrosive environments.

Microstructural evolution in 12% Cr heat-resistant steel during compression deformation at 650°C

Microstructural evolution in 12% Cr heat-resistant steel during compression deformation at 650°C

Quartz fluid inclusions and trace elements in the Lailisigaoer porphyry Mo deposit, Western Tianshan, Xinjiang: Fluid evolution and metallogenic mechanism in magmatic-hydrothermal system

The Lailisigaoer deposit is a typical porphyry Mo deposit located in the late Paleozoic Boluokenu metallogenic belt of Western Tianshan, NW China. This study aims to understand molybdenum mineralization and the dynamics of magmatic-hydrothermal fluid within the porphyry system, focusing on fluid inclusion, cathodoluminescence textures, and trace elemental composition in various generations of quartz. Six vein types in the Lailisigaoer deposit are classified as comb quartz veins with unidirectional solidification texture (UST, QI), actinolite/biotite ± quartz veinlets (M-type, QII), quartz-chalcopyrite vein (A-type, QIII), quartz-molybdenite vein (B-type, QIV), quartz-pyrite vein (D-type, QV) and quartz-carbonate vein (E-type, QVI). Micro thermometry data indicate decreasing homogenization temperatures in primary fluid inclusions from UST to E-type veins. The magmatic-hydrothermal fluids associated with UST and M-, A-, B-, D-, E-type veins underwent a transition from high temperature (342–495℃), high-pressure (∼1.25 kb), and variable salinity (6.7–41.1 wt%NaCl) in the H2O-CO2-NaCl system to low-temperature (142–238℃), low-pressure (∼0.25 kb), and low-salinity (1.6–5.1 wt%NaCl) in the H2O-NaCl system. This evolution is reflected in the proportion of quartz with oscillatory zones decreasing and irregular quartz increasing, indicating a shift from turbulent to stable fluid conditions. Furthermore, a gradual reduction in Ti concentration (from 79 ppm in UST to 1.4 ppm in E-type quartz) suggests a decrease in fluid temperature during the magmatic-hydrothermal evolution. Mineralization primarily occurs in A- and B-type veins, with molybdenum precipitation attributed to fluid immiscibility in a medium–high temperature (240–368 ℃) and high pressure (∼0.95 kb) environment. The A-type veins (mean 31 ppm in Ti concentrations) consist of equigranular (dark-core) (QIII-1) and patchy inhomogeneous CL-gray quartz (QIII-2). The B-type veins (mean 24 ppm in Ti concentrations) are characterized by equigranular (bright-core) inhomogeneous quartz (QIV-1) with growth zones that are cemented by later mosaic homogeneous CL-gray quartz (QIV-2). Based on the quartz-Ti thermometer, the mineralized veins (A- and B-type) were confined to be formed at depths of 2.8–3.6 km, with molybdenum mineralization occurring at 3.4–3.6 km. Molybdenum mineralization initiates during the QIV-1 crystallization period in magmatic-hydrothermal fluids and terminates in the QV-2 generation.

The effect of pressure on the thermodynamic properties of hydrogenic impurity in the GaAs semiconductor quantum well

ABSTRACT Studying the thermodynamic properties of hydrogen impurity in low-dimensional nanostructures under high-pressure environment is crucial for understanding the optical property and thermal excitation behaviour of semiconductor material. Here, we extensively explore the effect of pressure on thermodynamic properties, specifically, the average energy, free energy, entropy, and heat capacity of one-dimensional (1-D) hydrogenic impurity in GaAs semiconductor quantum well. Our findings reveal some novel phenomenon in the thermodynamic properties of hydrogenic impurity as pressure increases in the GaAs quantum well. Remarkably, at a constant temperature, both the average energy and free energy of hydrogenic impurity decrease as pressure rises, while entropy increases with increasing pressure. Intriguingly, the heat capacity shows distinct behaviour with varying pressure for different sizes of the quantum well. For very small size of the quantum well, the heat capacity increases with increasing pressure. However, for larger size of the quantum wells, the variation of heat capacity with pressure becomes irregular, showing a changeover from an increase to a decrease in response to increasing pressure. This research presents a pioneering method that employs pressure as a versatile tool for modulating the thermodynamic properties of hydrogenic impurity states in the nanostructures, and has some guidance for the preparation and synthesis of semiconductor devices.

Effective Underwater Drag Reduction: A Butterfly Wing Scale-Inspired Superhydrophobic Surface.

The microstructured superhydrophobic surface serves as an alternative strategy to decrease resistance of underwater vehicles, but the sustainment of an entrapped air layer and the stability of the corresponding gas-liquid interface within textures in flow shear or high pressure are still a great challenge. Inspired by the scales of Parantica melaneus wings, we propose a biomimetic surface with a hierarchical structure featuring longitudinal ridges and regular cavities that firmly pin the gas-liquid interface. The drag reduction rate of the Butterfly Wing Scale-Like Surface (BWSLS) demonstrates a noticeable rise over the single-scale textured mainstream biomimetic surfaces at moderate Reynolds numbers. The superior drag reduction mechanism is revealed as the synergistic effect of a thicker gas film and a more pronounced secondary vortex within the hierarchical textures. The former reduces the velocity gradient near the surface, while the latter decreases the vorticity and energy dissipation. In a high hydrostatic pressure environment, the proposed surface also demonstrates significant stability of the gas-liquid interface, with a gas coverage rate of over 67% during the cyclic loading, surpassing single-structured surfaces. Our study suggests promising surface designs for optimal drag reduction by mimicking and leveraging diverse surfaces of organisms adapted to oceanic climates.

A high-resolution characterization of surface film formed on alloys 800 and 690 exposed to chloride and thiosulfate-containing solution at 300°C

PurposeThis paper aims to characterize the surface film formed on Alloys 800 and 690 in chloride and thiosulfate-containing solution at 300°C.Design/methodology/approachAlloy 800 and 690 were immersed in chloride and thiosulfate-containing solution at 300°C up to five days, and then the surface film was analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy dispersive X-ray spectrometers (EDX).FindingsThrough static immersion experiments in a high-temperature and high-pressure water environment, the alloy samples covered by surface film after five days of immersion were obtained. The morphology of the surface film was characterized at both horizontal and cross-sectional scales using SEM and focused ion beam-TEM techniques. It was observed that due to the influence of the quartz lining, the surface film primarily exhibited a bilayered structure. The first layer contained a significant amount of SiO2, with a higher content of metal hydroxides compared to metal oxides. The second layer was predominantly composed of Fe, Ni and Cr, with a higher content of metal oxides compared to metal hydroxides.Originality/valueThe results showed that the materials of the lining of the autoclave could significantly influence the film composition of the tested material, which should be paid attention when analyzing the corrosion mechanism at high temperature.

The Impact of Impurity Gases on the Hydrogen Embrittlement Behavior of Pipeline Steel in High-Pressure H2 Environments.

The use of hydrogen-blended natural gas presents an efficacious pathway toward the rapid, large-scale implementation of hydrogen energy, with pipeline transportation being the principal method of conveyance. However, pipeline materials are susceptible to hydrogen embrittlement in high-pressure hydrogen environments. Natural gas contains various impurity gases that can either exacerbate or mitigate sensitivity to hydrogen embrittlement. In this study, we analyzed the mechanisms through which multiple impurity gases could affect the hydrogen embrittlement behavior of pipeline steel. We examined the effects of O2 and CO2 on the hydrogen embrittlement behavior of L360 pipeline steel through a series of fatigue crack growth tests conducted in various environments. We analyzed the fracture surfaces and assessed the fracture mechanisms involved. We discovered that CO2 promoted the hydrogen embrittlement of the material, whereas O2 inhibited it. O2 mitigated the enhancing effect of CO2 when both gases were mixed with hydrogen. As the fatigue crack growth rate increased, the influence of impurity gases on the hydrogen embrittlement of the material diminished.

Development of Machining Device with Real-Time Visualization of Boundary Surface on Tool Rake Face and Cutting Chip

Analysis of cutting phenomena has been conducted for a long time and many researchers have elucidated the phenomena that may occur at the cutting-edge during machining; for example, built-up edges and welding phenomena on cutting edge. However, the existing research has focused on observing the tool and chips after machining, when the tool and work material have been cooled, and are under atmospheric pressure. Therefore, we consider that it is different from the phenomenon that occurs during cutting. Because the cutting edge of a tool is in a high-temperature and high-pressure environment during machining and is released from such an environment after machining, the cutting edge must be visualized to discuss the actual cutting phenomena. There have been research reports in the past that have visualized the backside of cutting chips; however, that experiment was far from actual cutting phenomena and was conducted at significantly low cutting speed. Thus, the visualization of the cutting phenomenon is physically extremely difficult at the cutting edge. Under such circumstances, this study developed a device that observed the behavior of the boundary surface between cutting chips and the rake face in real time from the backside of the rake face during machining. By using the developed device, we could visualize this phenomenon to acquire the data directly and visually, which can otherwise be grasped only indirectly. In this device, a camera was mounted on a tool holder, and a cutting tip made of a transparent material was used to observe rake face, cutting edge, and flank face which can be visualized during machining from the backside of the rake face within one field of view. This paper reports on the outline of the developed device, its method, and the results of experimental observation of the state of two-dimensional cutting using a lathe.

TDG prediction model improvement by analysis and validation of experiments on a dam model.

The combination of aerated flows and a high-pressure environment in a stilling basin can result in the supersaturation of total dissolved gas (TDG) downstream of hydraulic projects, posing an ecological risk to aquatic populations by inducing gas bubble disease (GBD) or other negative effects. There is limited literature reporting TDG mass transfer experiments on a complete physical dam model; most existing research is based on measurements in prototype tailwaters. In this study, TDG mass transfer experiments were conducted on a physical model of an under-constructed dam, with TDG-supersaturated water as the inflow, and TDG concentrations were meticulously monitored within the stilling basin. The measurements indicate that the TDG saturation at the outlet of the stilling basin decreased by 13.7% and 10.6% compared to the inlet for the two cases, respectively. Subsequently, an improved TDG prediction model was developed by incorporating a sub-grid air entrainment model and a phase-constrained scalar model. The numerical simulation results were compared with experimental data, indicating a maximum error in TDG saturation at all measured points of less than ± 3%. Moreover, the TDG saturation showed an error of only ± 0.3% at the outlet of the stilling basin. This model has broad applicability to various flow types for obtaining TDG mass transfer results and evaluating mitigation measures of TDG supersaturation to reduce the harmful effects on aquatic ecosystems.

Investigation into the Heat Transfer Behavior of Electrostatic Atomization Minimum Quantity Lubrication (EMQL) during Grinding

Electrostatic atomization minimum quantity lubrication (EMQL) technology has been developed to address the need for environmentally friendly, efficient, and low-damage grinding of challenging titanium alloy materials. EMQL leverages multiple physical fields to achieve precise atomization of micro-lubricants, enabling effective lubrication in high temperature, high pressure, and high-speed grinding environments through the use of electric traction. Notably, the applied electric field not only enhances atomization and lubrication capabilities of micro-lubricants but also significantly impacts heat transfer within the grinding zone. In order to explore the influence mechanism of external electric field on spatial heat transfer, this paper first comparatively analyzes the grinding heat under dry grinding, MQL, and EMQL conditions and explores the intensity of the effect of external electric field on the heat transfer behavior in the grinding zone. Furthermore, the COMSOL numerical calculation platform was used to establish an electric field-enhanced (EHD) heat transfer model, clarifying charged particles’ migration rules between poles. By considering the electroviscous effect, the study reveals the evolution of heat transfer structures in the presence of an electric field and its impact on heat transfer mechanisms.

Art Education as a Healing Method Helps Sensitive Teenagers Grow up in Modern Chinese Family Education

With the Chinese society's emphasis on education, adolescent mental health problems have become increasingly prominent. Especially in the high-pressure family education environment, the emotional needs and psychological difficulties of highly sensitive adolescents are more prominent. This study not only focuses on the mental health of adolescents, but also aims to provide a new solution for family education and adolescent mental health through the unique perspective of art therapy. Art therapy integrates art and emotional connection to help promote the spiritual recovery of the individual. By exploring the restorative role of art in modern Chinese family education, we expect to provide new educational ideas for parents and educators, and promote the comprehensive and healthy development of adolescents.

Analysis on degassing at microgravity condition

For the future diversity and sustainability of the International Space Station, the manned flight time will be greatly increased, and the water required will be greatly increased as well. It is particularly important to deal with resources in more detail. In the process of treating drinking water, tiny air bubbles may be created. Bubbles can form in the Water Recovery and Management System (WRMS) on the ISS due to gas dissolution, microgravity environment, chemical reactions, and microbial metabolism. Water under pressure can dissolve gases. In the ISS, if water comes from a high-pressure environment to a lower one, gas may come out of solution, forming bubbles. Also, in the microgravity environment of the ISS, bubbles can remain suspended in the water, interfering with the systems sensors and pumps. Some processes in the water recovery system can produce gases as byproducts, such as electrolysis used in the Oxygen Generation System of the ISS. Finally, some microbial metabolic processes generate gases which can form bubbles in the water. According to four reasons given above, the passage will first introduce the current situation about dealing with bubbles in ISS, then providing some future directions of the development of the bubble-remove techniques.

The mechanism of granite breaking by electric pulse under high temperature and high pressure environment

AbstractHigh‐voltage electric pulse drilling technology has the advantages of high rock‐breaking efficiency, and low rock‐breaking energy consumption, which is one of the most promising rock‐breaking methods in geothermal drilling. However, there is insufficient understanding of the mechanism of high‐voltage electric pulse breaking of HDR under high‐temperature and high‐pressure environments (HTHP). In this paper, a numerical simulation model of electric breakdown under HTHP is constructed, and the whole process of high voltage electric pulse rock‐breaking and plasma channel generation is realized from the seven‐field coupling of circuit field, current field, magnetic field, breakdown field, heat transfer field, solid mechanics field and flow field. The temperature changes in the rock during the electric pulse rock‐breaking process were comprehensively analyzed, and the effects of different initial rock temperatures (200°C, 300°C, 400°C) and surrounding pressure conditions (30, 60, 90 MPa) on the high‐voltage electric pulse rock breaking law were considered. It is found that the thermal conductivity of the rock shows an increasing and then decreasing trend as the initial temperature of the rock increases, and that the thermal conductivity has a tendency to guide the development of plasma channels, and the radius of the plasma channels increases with the increase of the initial temperature of the rock. The heat transfer generated by high‐voltage electric pulse rock breaking is mainly in conduction, and the distribution shape of conduction heat is similar to the shape of the breakdown channel. The research in this paper can provide theoretical and technical guidance for developing electric pulse rock‐breaking technology.

Supporting newly qualified pharmacists in transitioning to independent practice: a qualitative analysis of the role of supervision

Abstract Introduction Newly qualified pharmacists (NQPs) face a demanding and challenging work environment during their transition to independent practice.[1,2] They also face challenges related to the changing nature of pharmacy practice, with pharmacists playing an increasingly important clinical role in patient care, which can be daunting for NQPs. Supporting NQPs during this transition period is essential for ensuring the sustainable development of health services. In 2021, Health Education England introduced the Newly Qualified Pharmacist Pathway, which included access to the Royal Pharmaceutical Society (RPS) e-Portfolio, formal learning of clinical and other skills, and access to educational supervision. The learning programmes were delivered by different providers in different settings/sectors. In hospitals, the Pathway was intended to complement existing programmes. Those in community pharmacy, general practice, community health services, health and justice, and care homes had access to a 12-month structured programme. Aim To discuss how supervision works and its contribution to supporting NQPs during their transition to independent practice. Methods Semi-structured qualitative interviews with NQPs (n=7) and supervisors (n=14). Email invitations were sent via learning providers. Participants were selected to capture NQPs and supervisors from various learning programmes and settings/sectors. Interviews were analysed thematically. Results The transition to independent practitioners meant NQPs were required to work with a high degree of autonomy in their practice. Yet, NQPs reported a lack of confidence in this. Supervisors reported that being an independent practitioner also meant that NQPs needed to be accountable for their decisions, learn to prioritise in a high-pressure environment, lead more experienced colleagues and manage a team. Supervision was an important part of the Pathway. Both NQPs and supervisors reported that supervisors provided NQPs with guidance, support, and feedback during their transition period. Supervisors added that they conducted learning needs assessments to foster a learner-centred approach that aided NQPs in expanding their skills and knowledge. They also supported NQPs in developing reflective practice as part of their professional development and progression to advanced practice. How supervision was conducted in practice varied across different settings/sectors. NQPs and hospital supervisors described that NQPs had a clinical work-based supervisor and an educational supervisor. In community pharmacies where NQPs often lacked access to support and structured learning opportunities, NQPs and supervisors claimed that remote educational supervision offered through the Pathway provided a support system for NQPs who would otherwise have been without any support structure. Conclusion Our study highlights that both NQPs and supervisors noted the importance of the support provided by educational supervisors to address learning/support needs in the early year of practice. However, the extent to which NQPs received what they needed varied widely. This support will likely become increasingly important from 2026, when pharmacists will require support as they become independent prescribers. We need to develop processes and infrastructure to ensure high-quality supervision is available to NQPs in all settings/sectors. The strength of the study lies in the in-depth interviews that provided rich and insightful data, effectively addressing the limitation posed by the relatively small number of participating NQPs.

Effects of perceived stress on turnover intention of female healthcare staff: a serial multiple mediation model

BackgroundHealthcare staff in China, especially females, work in a high-pressure, high-load, and high-risk environment, which affects the physical and mental health, the efficiency and quality of work, and increases turnover intention. The present study investigated the relationship between perceived stress and turnover intention in female healthcare staff, and the effects of future-oriented coping and work-family balance on this relationship.MethodsFour hundred thirty-five female medical workers were recruited to perform a perceived stress scale, future-oriented coping inventory, work-family balance scale and turnover intention scale. Meanwhile, serial multiple mediation analysis was performed using PROCESS.Results1) Perceived stress positively predicted the level of turnover intention in female healthcare staff; 2) Preventive coping and proactive coping showed mediation effects on the relationship between perceived stress and turnover intention, and preventive coping positively related to proactive coping; 3) The work-family balance also showed mediation effects on the relationship between perceived stress and turnover intention; 4) Preventive coping, proactive coping and work-family balance showed a serial multiple mediation on the relationship between perceived stress and turnover intention in female healthcare workers.ConclusionsPerceived stress affects the level of turnover intention in female healthcare staff through preventive coping, proactive coping, and work-family balance. In addition, the sequential model of future-oriented coping was validated among female healthcare staff.

Effects of compressive cyclic loading on the fatigue properties of oil-well cement slurries serving in deep downhole environments

With the increasing demand for energy from deep oil and gas reservoirs, oil-well cement slurries are subjected to complex compressive cyclic loading in high-temperature and high-pressure (HTHP) environments. Currently, no standard to guide the evaluation of the fatigue performance of cement slurries under cyclic loading or a systematic investigation to help understand it exists. To fill this gap, this study used a set of innovative HTHP curing and testing devices to mimic the actual operating conditions of deep wells. Cement slurries were cast, cured, and subjected to quasi-static and cyclic loading tests at four downhole temperatures (25, 90, 115, and 140 °C). In the cyclic-loading tests, three loading levels (30%, 50%, and 70%) under 20 MPa confining pressure were applied to study the fatigue performance, and nuclear magnetic resonance (NMR) was employed to identify internal microcrack damage. When the downhole temperature increased from 25 to 140 °C and the cyclic loading level increased from 30% to 70%, the accumulated plastic strain of samples increased by 13.8 times. A large increase in the plastic strain of oil-well cement slurries can significantly reduce the fatigue resistance and service life of oil and gas wells. Based on this research, the authors propose the addition of compressive cyclic loading tests (particularly under HTHP testing conditions) to the current oil-well cement slurry testing standards, which will be very significant for the fatigue performance evaluation of cement slurries used in HTHP environments in deep wells.

Kinetics and hydrothermal combustion characteristics of ethanol in supercritical water

Supercritical hydrothermal combustion is a novel, clean, and efficient combustion method. In this work, a mechanism-based kinetic model of ethanol appropriate for high-pressure hydrothermal environment was developed. Combined with theoretical analysis and continuous ignition experiments, the transient ignition process, ignition temperature, and extinction temperature were discussed. A turbulent combustion model coupling detailed kinetics was constructed to analyze the co-flow diffusion hydrothermal flame. It was found that the ethanol kinetic model can well predict the reaction process, critical ignition temperatures, extinction temperatures, and diffusion combustion process of hydrothermal combustion. The ignition temperatures of 2.40–5.72 wt% ethanol ranged between 500–390 °C, and OH was a significant ignition indicator. As an auxiliary fuel, ethanol is superior to methanol. During co-flow hydrothermal combustion, the interfacial reaction between fuel and oxidant in jet core area had an important influence, and the local high-temperature flame was mainly distributed near the downstream of fuel jet.

Study on Corrosion Fatigue Behavior of 304L Austenite Stainless Steel in 325 °C High-Temperature Water Environment

The fatigue crack growth behavior of 304L austenitic stainless steel (SS) in a 325 °C high-temperature and high-pressure water environment were investigated by a corrosion fatigue test system, by electron back scatter diffraction (EBSD), and by a transmission electron microscope (TEM). The experimental results indicated that the crack growth rate (CGR) of 304L SS increases with increasing the stress intensity factor, stress level, and fatigue frequency (f). Compared to dissolved hydrogen (DH) in a high-temperature water environment, dissolved oxygen (DO) significantly enhances the CGR by about an order of magnitude higher. The crack tip of 304L SS after the corrosion fatigue test under higher stress levels is sharper, with more secondary cracks on the fracture surface, while the crack tip under lower stress levels is blunter with relatively fewer secondary cracks. The oxidation behavior at the crack tip was analyzed under different loading and water chemistry conditions, and a related effect on the crack tip and CGR was clarified.