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fatigue crack propagation
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Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 570-579, October 21–24, 2019,
... Abstract Single crystal Ni-base superalloys are subjected to tension hold at high temperature in addition to cyclic loading during the operation of gas turbines. Various studies have investigated creep-fatigue crack propagation in superalloys under trapezoidal loadings and evaluated the life...
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Single crystal Ni-base superalloys are subjected to tension hold at high temperature in addition to cyclic loading during the operation of gas turbines. Various studies have investigated creep-fatigue crack propagation in superalloys under trapezoidal loadings and evaluated the life time based on parameters such as creep J-integral. However, it is still unclear how damage field and stress-strain condition change at the crack tip during hold time, and how it affects on fatigue crack propagation. In this study, the influence of the tension hold and accompanying creep at crack tip on subsequent fatigue crack propagation behavior was evaluated by introducing single tension holds into pure cyclic loadings. The series of the experiments revealed that because of the tension hold, material degradation and stress relaxation occurred simultaneously ahead of crack tip. In the region where material was degraded, the resistance against crack propagation was reduced, while in the region where stress was relaxed, the crack driving force was lowered.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 535-545, October 21–24, 2019,
... Abstract In this study, fatigue crack propagation behavior at lower temperature in single crystal nickel-base superalloys was investigated experimentally and analytically. Four types of compact specimens with different combinations of crystal orientations in loading and crack propagation...
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In this study, fatigue crack propagation behavior at lower temperature in single crystal nickel-base superalloys was investigated experimentally and analytically. Four types of compact specimens with different combinations of crystal orientations in loading and crack propagation directions were prepared, and fatigue crack propagation tests were conducted at room temperature and 450°C. It was revealed in the experiments that the crack propagated in the shearing mode at room temperature, while the cracking mode transitioned from the opening to shearing mode at 450°C. Both the crack propagation rate and the transition behavior were strongly influenced by the crystallographic orientations. To interpret these experimental results, crystal plasticity finite element analysis was carried out, taking account some critical factors such as elastic anisotropy, crystal orientations, 3-D geometry of the crack plane and the activities of all 12 slip systems in the FCC crystal. A damage parameter based on the slip plane activities derived from the crystal plasticity analysis could successfully rationalize the effect of primary and secondary orientations on the crystallographic cracking, including the crack propagation paths and crack propagation rates under room temperature. The proposed damage parameter could also explain the transition from the opening to crystallographic cracking observed in the experiment under 450°C.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 610-621, October 11–14, 2016,
... Abstract The fatigue crack propagation thresholds of SAW weld metal of 25Cr2Ni2MoV simulating product of fossil and nuclear power low pressure turbine rotor at different stress ratios are tested. There is a big dispersity of the test results, even at the same stress ratio. The double logarithm...
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The fatigue crack propagation thresholds of SAW weld metal of 25Cr2Ni2MoV simulating product of fossil and nuclear power low pressure turbine rotor at different stress ratios are tested. There is a big dispersity of the test results, even at the same stress ratio. The double logarithm curves of the fatigue crack growth rate and stress intensity factor range are researched. The difference of critical points between stable propagation region and near-threshold region in different specimens is found to be an important cause to the dispersity. Their locations in the specimens can be determined by the method of backward inference. After the observation of the microstructures around the critical points, a good correspondence between the size of prior austenite grain and the maximum size of monotonic plastic zone on the crack tip is confirmed. The difference of the critical points at the same stress ratio is caused by the inhomogeneous microstructures. So the inhomogeneous microstructures in the multi-pass and multi-layer weld metal contribute to the dispersity of the experimental threshold values.
Proceedings Papers
The Fracture Behaviors of the Welded Joints in P92, P122 and P23 Pipe Steels for Fossil Power Plants
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 930-949, October 25–28, 2004,
... Abstract This paper reports on a study that investigated how low cycle fatigue (LCF) and fatigue crack propagation (FCG) properties of P92, P122, and P23 steels vary between 600°C and 700°C depending on the location relative to a cross weld. Microstructure analysis was also performed...
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This paper reports on a study that investigated how low cycle fatigue (LCF) and fatigue crack propagation (FCG) properties of P92, P122, and P23 steels vary between 600°C and 700°C depending on the location relative to a cross weld. Microstructure analysis was also performed on fractured specimens. Due to its higher yield strength, P122 exhibited the best continuous LCF life. However, creep-fatigue interaction (CFI) in the weld heat-affected zone (HAZ) of P122 and P23 steels significantly reduced their lifespans compared to continuous LCF tests. This reduction is attributed to the effect of weld thermal cycles on fine precipitates. FCG tests revealed that the base metal consistently outperformed the HAZ in all tested steels and temperatures. P92 and P122 showed similar FCG rates except for P92's behavior at 600°C, which resembled P23. In both steels, the HAZ exhibited faster FCG rates at 600°C and 700°C compared to the base metal, particularly at lower stress intensity factor ranges (ΔK). Within the HAZ, the region 1 mm from the fusion line displayed the slowest FCG rates, followed by the base metal, while the fusion line and the region 2 mm from it showed the fastest. Fracture surfaces near the fusion line displayed cleavage-like features, while the region 1 mm away exhibited features associated with higher crack growth resistance.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 1-10, October 21–24, 2019,
... of conventional and novel steels were investigated in thermo-mechanical fatigue and fatigue crack propagation experiments. Based on the results, improved, ferritic “HiperFer” (High performance Ferrite) steels were designed, produced and characterized. A brief description of the current state of development...
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Future, flexible thermal energy conversion systems require new, demand-optimized high-performance materials. In order to provide a basis for the targeted development of fatigue-resistant, cost-effective steel grades, the microstructural damage to materials and the failure of conventional and novel steels were investigated in thermo-mechanical fatigue and fatigue crack propagation experiments. Based on the results, improved, ferritic “HiperFer” (High performance Ferrite) steels were designed, produced and characterized. A brief description of the current state of development is given.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 483-494, October 15–18, 2024,
... of physically short cracks. This allows the evaluation of the behavior of both near-surface and internal defects that are not accessible to the atmosphere. crack propagation fatigue crack growth finite element simulation gas turbine blades high cycle fatigue laser powder bed fusion nickel-based...
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For the safe life prediction of components under high cycle fatigue loading at high temperature, such as gas turbine blades and turbocharger components, the behavior of initial defects, which are physically short cracks below the long crack threshold ΔK is of crucial importance. The evolution of different crack closure mechanisms (such as plasticity, roughness and oxide induced crack closure) can lead to crack arrest by a reduction of the effective crack tip loading. To visualize the crack growth behavior of such cracks, cyclic crack resistance curves (cyclic R-curves) are used. The experimental determination of cyclic R-curves is challenging, especially under high temperature conditions due to a lack of optical accessibility. The formation of very short cracks in high strength materials makes it even more complicated to reliably determine these data. Within this study the crack growth behavior of physically short fatigue cracks in three different material states of the nickel alloy IN718 (wrought, cast and PBF-LB/M - processed) is experimentally determined at 650 °C. Based on a load increase procedure applied on Single Edge Notched (SEN) specimens with a compression pre-cracking procedure in advance, crack propagation of physically short cracks is measured with alternating current potential drop systems in air and under vacuum conditions. These examinations are carried out for three different load ratios (R = -1, 0 and 0.5) to investigate the amount of certain crack closure mechanisms active under different loading conditions. Moreover, the formation of a plastic wake along the crack flanks is determined by a finite element simulation. The results determined in air and under vacuum conditions are used to describe the impact of oxide induced crack closure on the behavior of physically short cracks. This allows the evaluation of the behavior of both near-surface and internal defects that are not accessible to the atmosphere.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 517-527, October 15–18, 2024,
... them potentially transformative for future energy technologies. This paper examines the microstructural mechanisms underlying HiperFer’s enhanced fatigue resistance in both short and long crack propagation, while also presenting current findings on salt corrosion properties and exploring potential...
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High-performance Ferritic (HiperFer) steels represent a promising materials innovation for next-generation thermal energy conversion systems, particularly in cyclically operating applications like concentrating solar thermal plants and heat storage power plants (Carnot batteries), where current market adoption is hindered by the lack of cost-effective, high-performance materials. HiperFer steels demonstrate superior fatigue resistance, creep strength, and corrosion resistance compared to conventional ferritic-martensitic 9-12 Cr steels and some austenitic stainless steels, making them potentially transformative for future energy technologies. This paper examines the microstructural mechanisms underlying HiperFer’s enhanced fatigue resistance in both short and long crack propagation, while also presenting current findings on salt corrosion properties and exploring potential alloying improvements for fusion reactor applications, highlighting the broad technical relevance of these innovative materials.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 90-100, October 11–14, 2016,
...-10CrMoV steels already applied in different types of turbines successfully. Heavy cyclic loading getting more importance than in the past results in utilization of the fatigue capabilities at high and low temperatures which might lead to crack initiation and subsequent crack propagation. Fracture...
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There are main drivers for the design and assessment of steam turbine components of today such as demands for improved materials, higher plant cycling operation, and reduced life-cycle costs. New materials have been developed over the last decades resulting in advanced martensitic 9-10CrMoV steels already applied in different types of turbines successfully. Heavy cyclic loading getting more importance than in the past results in utilization of the fatigue capabilities at high and low temperatures which might lead to crack initiation and subsequent crack propagation. Fracture mechanics methods and evaluation concepts have demonstrated their applicability to assess the integrity of components with defects or crack-like outage findings. Based on realistic modelling of the failure mechanism, accurate prediction of crack sizes at failure state can be improved defining the appropriate damage criteria. Ductility is a main aspect for robust design but its value definition can depend on component type, design rules, real loading conditions, service experience, and material characteristics. The question which direct material parameter is able to serve as limit value in design and how it can be determined has to be solved. Examples of advanced analysis methods for creep crack growth and fatigue interaction involving the crack initiation time show that the reserves of new martensitic 9-10Cr steels in high temperature application can be well quantified. The creep rupture elongation A u and the loading conditions in the crack far field are main factors. If the A u value is sufficient high also after long-time service, the material remains robust against cracks. Investigations into the influence of stress gradients on life time under fatigue and creep fatigue conditions show that e.g. for 10CrMoWV rotor steel crack growth involvement offers further reserves. The consideration of constraint effect in fracture mechanics applied to suitable materials allows for further potentials to utilize margin resulting from classical design. The new gained knowledge enables a more precise determination of component life time via an adapted material exploitation and close interaction with advanced design rules.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 429-440, October 15–18, 2024,
... was unknown. As shown in Figure 8b) fatigue crack propagation was near the upper scatter band from tests done in the German HTR program. At 620 °C and lower, better crack propagation behavior could be observed. From this, it can be concluded that the material is of higher strength. The crack propagation rates...
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This paper reports on the latest in a series of projects aiming at the qualification of new and proven materials in components under a severe service environment. In the initial stages of the project (HWT I & HWT II), a test loop at Unit 6 of the GKM Power Plant in Mannheim was used to study the behavior of components for advanced ultra-supercritical (A-USC) plants made from nickel alloys at 725 °C under both static and fluctuating conditions. Due to recent changes in the operation modes of existing coal-fired power plants, the test loop was modified to continue operating the existing nickel components in the static section while applying thermal cycles in a different temperature range. HR6W pipes and valves were added to the bypass of the static section, and all components in the cyclic section were replaced with P92, P93, and HR6W components. The test loop achieved approximately 9000 hours of operation and around 800 cycles with holding times of 4 and 6 hours. After dismantling the loop, nondestructive and destructive examinations of selected components were conducted. The accompanying testing program includes results from thermal fatigue, fatigue, thermal shock, and long-term creep tests, focusing on the behavior of base materials and welds, particularly for HR6W, P92, P93, and other nickel-based alloys. Additionally, test results on dissimilar welds between martensitic steel P92 and nickel alloys A617 and HR6W are presented. Numerical assessments using standardized and numerical lifetime estimation methods complement the investigations. This paper provides insights into the test loop design and operational challenges, material behavior, and lifetime, including advanced numerical simulations and operational experiences with valves, armatures, piping, and welds.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 351-359, October 22–25, 2013,
... Abstract This paper presents the creep and creep-fatigue crack growth behaviors of 30Cr1Mo1V turbine rotor steel which had been in service for 16 years. Two typical sections of the rotor, i.e. high and low temperature sections, are examined at 538°C, with crack initiation and propagation...
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This paper presents the creep and creep-fatigue crack growth behaviors of 30Cr1Mo1V turbine rotor steel which had been in service for 16 years. Two typical sections of the rotor, i.e. high and low temperature sections, are examined at 538°C, with crack initiation and propagation monitored by D.C. potential drop method in a compact tension (CT) specimen. The material of the high temperature section has the lower resistance to creep and creep-fatigue crack growths than the low temperature section. The creep crack initiation (CCI) time decreases with the increase of initial stress intensity factor. The creep-fatigue crack growth (CFCG) is dominated by the cycle-dependent fatigue process when the hold time at the maximum load is shorter, but it becomes dominated by the time-dependent creep process when the hold time becomes longer. The high temperature section shows a larger influence of time-dependent creep behavior on CFCG than the low temperature section.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 488-495, October 21–24, 2019,
... are known to have susceptibility to brittle cracking under hold-time fatigue in air. Literatures regarding fatigue crack growth suggest that oxygen diffusion at grain boundary during hold-time or under low frequency assists crack propagation and consequently cracks behave as time-dependent [1]. In air...
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This study aims to examine the effects of grain boundary oxidation and creep on crack initiation and fracture behaviors in cold worked surface layer, under static tensile stresses in air. To determine these effects in relation to percent cold work and hardness scale, cold-rolled plates with a reduction ratios between 10% and 50% were prepared. Uniaxial constant load (UCL) tests were conducted at elevated temperature in air using smooth round bar specimen. UCL tests with a load of 0.9σy (926MPa) at 550°C show that rupture time for all cold- rolled materials were shorter than that of as-received material. From cross-sectional observation after UCL testing, surface crack at grain boundary and voids were observed in as-received material, whereas creep cracks were also observed in cold-rolled materials. This implied that crack initiation was assisted by cold working. Comparing test results with a load reduced to 0.8σy (823MPa), difference of rupture time was expected as a factor of 5 for as-received material, and measured as 2-3 for cold-rolled materials. It was suggested that cold worked layer was more sensitive to creep than base metal.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 180-189, October 22–25, 2013,
.... This article shows results of currently investigated nickel-based alloys for newly developed headers, pipes and other high temperature boiler applications and their critical creep crack propagation behavior. A-USC power plants creep crack growth headers high temperature boilers nickel-based alloys...
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To improve efficiency and flexibility and reduce CO 2 emissions, advanced ultra super critical (AUSC) power plants are under development, worldwide. Material development and its selection are critical to the success of these efforts. In several research and development programs / projects the selection of materials is based on stress rupture, oxidation and corrosion tests. Without doubt, these criteria are important. To improve the operational flexibility of modern power plants the fatigue properties are of increased importance. Furthermore, for a safe operation and integrity issues the knowledge about the crack behavior is essential. Crack initiation and crack growth may be caused by natural flaws or cracks induced by component operation. In order to develop new materials, properties like tensile strength and creep strength are an important part of qualification and subsequent approval by notified bodies. Consequently short term properties as well as time-temperature dependent properties are generated and taken into considerations. In the case of high strength γ'-strengthening nickel-base alloys investigating the creep crack behavior is also strongly recommended. This article shows results of currently investigated nickel-based alloys for newly developed headers, pipes and other high temperature boiler applications and their critical creep crack propagation behavior.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 260-270, October 11–14, 2016,
... transgranular at the edges of the holes on the inner surface, propagate also mainly transgranular into the base material (Fig. 6 and 7). The multiple cracks found are characteristic for (thermal)-fatigue damage. The intergranular contribution to crack growth was very low in both material regions. In the area...
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In the test loop HWT II (High Temperature Materials Test Loop) installed in the fossil power plant Grosskraftwerk (GKM) Mannheim in Germany, thick-walled components made of nickel base alloys were operated up to temperature of 725 °C. The operation mode chosen (creep-fatigue) was to simulate a large number of start-ups and shutdowns with high gradients as expected for future high efficient and flexible power plants and to investigate the damage due to thermal fatigue of the used nickel base alloys. In this paper the damage evolution of a header made of the nickel base alloys Alloy 617 B and Alloy C263, which was a part of HWT II test rig, were investigated using nondestructive and destructive techniques. Furthermore, the damage has been considered and evaluated by using numerical methods. In addition, different lifetime assessment methods of standards and recommendations with focus on creep-fatigue damage were used and evaluated. The different lifetime models are applied to the header and the results were compared to the results of metallographic investigations and damage observations.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 254-264, October 22–25, 2013,
... hold time upto 500 seconds were introduced at 750°C by applying trapezoidal waveform. Fracture surfaces were examined by optical and scanning electron microscope to determine the fatigue crack initiation and propagation modes. Studies were also conducted on longitudinal section of the specimen...
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Significant development is being carried out worldwide for establishing advanced ultra supercritical power plant technology which aims enhancement of plant efficiency and reduction of emissions, through increased inlet steam temperature of 750°C and pressure of 350 bar. Nickel base superalloy, 50Ni-24Cr-20Co-0.6Mo-1Al-1.6Ti-2Nb alloy, is being considered as a promising material for superheater tubes and turbine rotors operating at ultra supercritical steam conditions. Thermal fluctuations impose low cycle fatigue loading in creep regime of this material and there is limited published fatigue and creep-fatigue characteristics data available. The scope of the present study includes behavior of the alloy under cyclic loading at operating temperature. Strain controlled low cycle fatigue tests, carried out within the strain range of 0.2%-1%, indicate substantial hardening at all temperatures. It becomes more evident with increasing strain amplitude which is attributed to the cumulative effects of increased dislocation density and immobilization of dislocation by γ′ precipitates. Deformation mechanism which influences fatigue life at 750°C as a function of strain rate is identified. Hold times up to 500 seconds are introduced at 750°C to evaluate the effect of creep fatigue interaction on fatigue crack growth, considered as one of the primary damage mode. The macroscopic performance is correlated with microscopic deformation characteristics.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 747-758, October 11–14, 2016,
... was a groove from the machining. The other initial part was a corrosion fatigue mechanism with corrosion pittings detected in surface around the main crack. The corrosion fatigue starts at several point with corrosion pitting which initiated cracks in the tip of the pitting. The small cracks propagated...
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A failure of the upper casing of the circulation pump led to a big damage in the PP Staudinger unit 5 on 12th of May 2014. According to the §18(2) BetrSichV an extensive root cause analysis (RCA) was started. From the beginning on different lines of activities were initiated to handle the situation with the required diligence. Decisions were made, taking into account safety regulations, possibility of repair and best practice engineering. Following the board decision to repair the unit 5, a lot of detailed work was done. All of the performed work packages were linked in different timelines and needed to meet in the key points. Consequently it was a challenge to achieve the agreed date of unit 5 restart on 15th of January 2015. The unit restart on the targeted date was a proof of the excellent collaboration between all involved parties. The presentation gives a summarizing overview about the damage, the main results of the RCA and the repair activities.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 1351-1360, October 21–24, 2019,
... of the Charpy specimens of the present 10% Cr steel and P92-type steel fractured at nearly the same temperatures of 10 and 20 C, respectively, in the stable crack propagation region are shown in Fig. 7. The distinct difference in the microvoid formation in these steels is clearly seen in Fig. 7. The voids...
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9-12%Cr martensitic steels can be applied to the next highest temperature components such as boiler tracts, steam pipelines and turbines of advanced ultra-supercritical power plants with steam temperatures of 650°C. New 10%Cr martensitic steels with high B and low N contents can be a worthy candidate for use in production because it has superior creep resistance. At the same time, resistance to cyclic and dynamic loads is very important. In this work, we studied the low cycle fatigue (LCF) properties at room and elevated (500-650°C) temperatures and Charpy impact toughness at temperatures ranging from -196…100°C of advanced 10% Cr martensitic steel with high B and low N contents. The effect of new alloying scheme and corresponding peculiarities of M 23 C 6 carbides on the low cycle fatigue resistance and impact toughness of the 10%Cr martensitic steel is analyzed. It is revealed that fine and densely distributed carbides has no effect on the fatigue resistance except for the slight improvement of fatigue life at small strain amplitudes and shift the ductile-brittle transition temperature (DBTT) to higher but satisfactory value of +10°C as compared to other high-chromium martensitic steels.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 653-671, October 25–28, 2004,
... creep processes affect pre-existing defects is essential for ensuring long-term component integrity. crack propagation creep crack initiation creep-fatigue interaction life assessment martensitic stainless steel thermal efficiency ultra super critical power plants httpsdoi.org/10.31399...
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New martensitic steels (9-10 CrMoNi(W)VNbN) are being developed for ultrasupercritical power plants to achieve higher efficiency and reduced environmental impact. Improved life assessment methods are crucial for the safe and economical long-term operation of these high-temperature components. This includes gathering creep, creep-fatigue, and crack data to establish design curves, as well as advanced modeling to predict deformation and lifetime. Complex experiments under various loading conditions and multiaxial behavior are necessary for verification. Furthermore, understanding how creep processes affect pre-existing defects is essential for ensuring long-term component integrity.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 405-415, October 21–24, 2019,
... (J-R) with multiple-sample method by using a mechanical testing machine (MTS Landmark 1). Figure 1 shows the sampling location and dimensions of compact tension sample manufactured according to the international standard ISO 12135 [18]. The samples were fatigue pre-cracked at room temperature...
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In the present study, the Inconel 617B superalloy welded trial rotor was fabricated by narrow gap tungsten inert gas (NG-TIG) welding and the effects of temperature on fracture toughness of its welded joint were investigated at 650 ℃ and 730 ℃. Fracture toughness (J0.2) of the base metal was much higher than that of the weld metal at the same temperature, which was attributed to its excellent macroscopical plasticity and the interactions of strain localization, misorientation, and coincidence site lattice (CSL) boundaries. For the base metal, the value of J0.2 was higher at 730 ℃ than at 650 ℃, resulting from the appreciable increase in ductility and decrease in strain localization as the temperature increased. For the weld metal, higher temperature (730 ℃) reduced strength but hardly improved plasticity, and the regions of high strain localization uniformly distributed in the weld metal, resulting in completely tearing the whole interface apart and lower fracture toughness of the weld metal.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 750-761, October 21–24, 2019,
... and vacuum at different frequencies [23]. Their work showed that, depending on the test conditions, fatigue failure in A286 can occur in intergranular or transgranular or even mixed mode fashion. Wu et al. reported that under high stress cycles, cracks monotonously propagate to failure in A286 [24]. However...
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The A286 is one of the earliest superalloys developed. It has been used for manufacturing different components of turbo machineries because of its balanced high temperature properties. These components include shafts, discs, spacers, blades and fasteners. This paper reviews some of the issues and recent field experiences related to metallurgy, fabrication, in-service evaluation and failure of some of these components. The fabrication aspects including the effects of alloy melting processes, forging parameters and different types of heat treatments on the processed parts are discussed. The importance of these factors on the microstructure and properties of A286 are highlighted. The effects of service exposure on some of these parts are also discussed. In service evaluation involves checking for service induced damage or changes in microstructures and properties so that the suitability of the part for continued service can be determined. The failure analysis section of the paper briefly discusses failures of two expander wheels and an expander disc made out of A286 to pinpoint some of the salient features of damage accumulation and fracture during service.
Proceedings Papers
AM-EPRI2010, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Sixth International Conference, 450-469, August 31–September 3, 2010,
... conditions, the time required for a fatigue crack to initiate and to propagate to fracture was determined. Specimens were load-cycled within the test chamber at an ultrasonic (19KHz) frequency. This allowed the minimum cyclic load for the given conditions to be determined. The specimens were observed...
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A research program has been initiated to develop the first predictive methodology for corrosion fatigue life in steam turbine blades, addressing a critical gap in current understanding despite extensive research into corrosion pitting and fatigue failure. The study focuses initially on dual-certified 403/410 12% Cr stainless steel, utilizing a newly developed test facility capable of conducting high-cycle fatigue tests in simulated steam environments at 90°C with controlled corrosive conditions. This testing platform enables the investigation of various steady and cyclic stress conditions, establishing a foundation for future testing of other blade steels and the development of comprehensive blade life estimation techniques.
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