High Temperature Creep Rupture Research Articles

Tracking research on the performance changes of S31042 steel under long term service

Tracking research on the performance changes of S31042 steel under long term service

High-temperature creep rupture behavior of dissimilar welded joints of RAFM steel and 316L steel by friction stir welding

High-temperature creep rupture behavior of dissimilar welded joints of RAFM steel and 316L steel by friction stir welding

Tensile and creep resistance improvement of GH4975 alloy for turbine discs via electron beam smelting layer solidification technology

Tensile and creep resistance improvement of GH4975 alloy for turbine discs via electron beam smelting layer solidification technology

High-Temperature Creep and Microstructure Evolution of Alloy 800H Weldments with Inconel 625 and Haynes 230 Filler Materials

Alloy 800H stands as one of the few code-qualified materials for fabricating in-core and out-of-core components operating in high-temperature reactors. Welding is a common practice for assembling these components; however, the selection of a suitable filler material is essential for enhancing the high-temperature creep resistance of Alloy 800H weldments in high-temperature applications. In this study, Inconel 625 and Haynes 230 filler materials were used to weld Alloy 800H plates by employing the gas tungsten arc welding technique. The high-temperature tensile and creep rupture properties, microstructural stability, and evolution of the weldments after high-temperature exposure were investigated and compared with those of Alloy 800H. The results show that both weldments exhibit enhanced tensile and creep behavior at 760 °C. The creep rupture times of the weldments with Inconel 625 filler and Haynes 230 filler materials were about two and three time longer, respectively, than those of Alloy 800H base metal when tested at 80 MPa and 760 °C. Carbides (MC and M23C6) were commonly observed in the microstructures of both the weld and base metals in the two weldments after high-temperature creep tests. However, the Inconel 625 filler weldment displayed detrimental δ and Laves phases in the fusion zone, and these precipitates could be potential sites for initiating cracks following prolonged high-temperature exposure. This study shows that the weldment with Haynes 230 filler material exhibit better phase stability and creep rupture properties than the one with Inconel 625, suggesting its potential for use as a candidate filler material for Alloy 800H for further investigation. This finding also emphasizes the critical consideration of microstructural evolutions and phase stability in evaluating high-temperature materials and their weldments in high-temperature reactor applications.

Influence of Ru on high-temperature creep rupture properties and oxidation behavior of Ni-based single-crystal superalloys

Influence of Ru on high-temperature creep rupture properties and oxidation behavior of Ni-based single-crystal superalloys

Creep and stress relaxation experiments of 1960-grade high-strength steel wire at elevated temperatures

Creep and stress relaxation experiments of 1960-grade high-strength steel wire at elevated temperatures

Influence of laser power on the high-temperature creep rupture life of 304L stainless steel manufactured by selective laser melting

Influence of laser power on the high-temperature creep rupture life of 304L stainless steel manufactured by selective laser melting

Design and application of double stove wires high-temperature furnace in high-temperature creep rupture test

This paper presented a high-temperature furnace with double electric stove wires for the test of high-temperature creep rupture, adopted the 5 mm electric stove wire in diameter, and the wires are made up of the working stove wire and the alternate stove wire. When the tester system detects the working stove wire is fractured, it will automatically and quickly switch the power supply circuit from the working stove wire to the alternate stove wire. Then the alternate stove wire starts to heat to keep the high-temperature furnace working, reducing the loss caused by the interruption of the test on account of the fractured stove wire. Experimental result indicates that the high-temperature furnace with double electric stove wires can solve the problem that when the stove wire is fractured, the test is difficult to proceed for a long time and high-temperature creep rupture test with the classical high-temperature furnace. Besides, the 5 mm in diameter electric stove wire can also meet the temperature control on the ultra-high-temperature (such as 1200 °C) Creep test.

Enhancing mechanical properties and creep performance of 304H and inconel 617 superalloy dissimilar welds for Advanced Ultra Super Critical power plants

Enhancing mechanical properties and creep performance of 304H and inconel 617 superalloy dissimilar welds for Advanced Ultra Super Critical power plants

Design of heat-resistant Al–Mg –Zn–Cu–Ni quinary alloy: Controlling intermetallic phases and mechanical performance at elevated temperature

Owing to good formability, wrought Al alloys are used in a wide range of industries, including turbochargers in automobile engines. The development of Al alloys with increased high-temperature strength is necessary to improve the fuel efficiency of engines. In this study, a modified heat-resistant Al–Mg–Zn–Cu–Ni quinary alloy with superior high-temperature strength and creep rupture life at 200 °C (potential temperature in service for compressor radial impellers) was designed. The thermodynamic assessments provided a modified alloy composition of Al–5Mg–3.5Zn–2Cu–2Ni (at %) exhibiting α-Al phase in equilibrium with T-Al6Mg11Zn11 and Al3(Ni, Cu)2 phases at elevated temperatures. The experimental alloy showed granular T and Al3(Ni, Cu)2 phases often located on grain boundaries in the α-Al matrix, although the undissolved Al3Ni phase (formed in solidification) locally remained. Apart from the T phase, the η-Zn2Mg phase containing Cu element preferentially precipitated on grain boundaries. A large number of fine precipitates were dispersed homogeneously in the grain interior after the aging at 200 °C or 300 °C. Compared to the base alloy with a ternary composition of Al–5Mg–3.5Zn (at %) and conventional Al alloys, the designed quinary alloy (pre-aged at 200 °C for 10 h) showed a high strength at elevated temperatures above 200 °C. The creep-rupture life at 200 °C/105 MPa was remarkably extended to 665 h by the addition of Cu and Ni elements into the base ternary alloy. The rupture life was more than ten times longer than one (57 h) of the ternary alloys. The alloy modification based on the thermodynamic calculations provides an effective approach for designing lightweight Al alloys with superior high-temperature strength and creep rupture life.

High-temperature creep rupture behavior of dissimilar welded joints in martensitic heat resistant steels

• High-temperature creep rupture behavior of F92/Co3W2 welded joints are studied. • Fracture position and mode change with creep testing conditions. • The evolution of creep damage micromechanisms is identified and discussed. • Extrapolating 100,000 h creep rupture strength satisfies the industrial need. • Temperature exhibits more obvious influence on creep life than stress. The creep rupture behavior and microstructure changes of dissimilar welded joints of two types of martensitic heat resistant steel F92 and Co3W2, under a creep testing of 115–200 MPa and 873–893 K, were investigated. Fracture position and mode change from transgranular ductile fracture in parent F92 to intergranular brittle fracture in the fine grain heat affected zone (type IV cracking) near F92, with the drop of applied stress. Microstructural degradation resulted from creep with respect to dislocation density decrease, precipitates coarsening, dislocation cells, microvoids, macroscopic secondary cracks, and fracture surface morphology are researched based on detailed experimental results. The creep rupture data are analyzed employing Norton’s power law, Monkman–Grant relation, creep damage tolerance, and Larson–Miller parameter. Main creep damage micromechanisms are analyzed with the aid of calculated and experimental data. The extrapolating creep rupture stress for a creep life of 100,000 h are obtained and the influence of stress change and temperature change on creep life are compared in terms of calculated normalized creep life growth rate.

Microstructures and high-temperature failure analyses of 25Cr-35Ni-Nb + MA/32Cr-20Ni-Nb dissimilar welded joint with different filler wires

• The dissimilar metal joints of 25Cr-35Ni-Nb + MA/32Cr-20Ni-Nb were welded by four different filler wires. • The microstructure, precipitate as well as the grain orientation of weld seams were studied and compared. • The optimum filler wire was recommended based on the uniformity of microstructure and high-temperature performance. To address the issue of lacking scientific guidance for welding 25Cr-35Ni-Nb + MA/32Cr-20Ni-Nb joint in petrochemical plant applications, the joint microstructures were studied by adopting four types of filler wires. The high-temperature tensile tests and creep rupture tests were performed to investigate joint failure mechanisms. Cellular/columnar dendritic grains were formed at the fusion line region with similar orientations to adjacent un-melted grains. The fine-sized dendritic grains generated at the central weld seam presented a larger misorientation owing to a lowered cooling rate. The lesser alloying element in filler wire led to a larger area with cellular/columnar dendritic grains. The carbide precipitates mostly located at grain boundaries either in the form of particles or necklace structures depending upon the filler wire compositions. The heterogeneous microstructure was thought to be the main reason for the failure at weld seam and fusion line region with large hardness fluctuations when joints welded by the filler wire with a more diverse alloying element. The filler wire with the least introduction of alloying elements, i.e., ERNiCrCoMo-1, gave rise to a more uniform microstructure and hence higher joint property without failing at the weld seam, which was therefore considered as the most suitable filler wire candidate.

Creep rupture life prediction of nickel-based superalloys based on data fusion

Creep rupture life is a key performance parameter of nickel-based superalloys, which directly affects the engineering service behavior of components. In this study, a machine learning method based on data fusion was proposed to predict the properties of new alloys with the properties of existing alloys, or to predict other related properties of the same alloy, so as to solve the problem of accurate prediction of creep rupture life caused by the lack of accumulated data. Using the existing nickel-based superalloy creep rupture life data accumulated in the NIMS database, a creep rupture life prediction model was established using key alloy factor screening and feature-based transfer learning strategy (FS-SVR). The performance of GH4169D alloy was successfully predicted by the properties of GH4169 alloy, and the high temperature creep rupture life was predicted by the low temperature creep rupture life of GH4169 and GH4169D alloys, and the prediction accuracy reached more than 90%. The research results not only provide a fast method for predicting the creep properties of novel nickel-based superalloys, but also provide a reference case for data fusion to assist the research and development of new materials.

Experimental investigation on high-temperature creep behavior of carbon fiber reinforced polymer cable

Both steady state-constant load and temperature (ST-CLT), and transient state-constant load and temperature (TR-CLT) tests were conducted on carbon fiber reinforced polymer (CFRP) cable in order to investigate the corresponding high-temperature creep behavior. The failure modes, creep strains and rupture times of CFRP cables exposed to high temperature were obtained in ST-CLT and TR-CLT tests, while the residual tensile strength and elastic modulus of specimens without rupture after high-temperature creep tests were determined by conducting high-temperature tensile tests . The variation law of high-temperature creep strains and rupture times of CFRP cable obtained from ST-CLT tests were compared to these of TR-CLT tests to identify the effect of temperature-load path. A practical model for characterizing the high-temperature creep behavior of CFRP cable was developed. Finally, the sustained stress levels and rupture times of specimens exposed to high temperature were analyzed to predict the high-temperature creep rupture stress level of CFRP cable. The obtained results indicated that the rupture morphology of high-temperature creep rupture specimens was the completely soft fiber bundles with “fluffy” pattern. The high-temperature creep strains of CFRP cables in ST-CLT and TR-CLT tests were highly depended on temperature, sustained stress level and time. The presence of pre-tension load before heating accelerated the damage of strength and stiffness for CFRP cable at high temperature, and the damage degree increased with the increasing sustained stress level and high-temperature. The developed practical models for CFRP cables under ST-CLT and TR-CLT conditions can accurately predict the high-temperature creep strains. In the fire resistant design of pre-stressed structures with CFRP cables, the effect of high-temperature creep rupture stress of CFRP cable was not negligible.

Microstructural evolution of Super304H stainless steel during high-temperature creep rupture

This study is aimed to explore the microstructural evolution of Super304H stainless steel during long-term creep. Creep-rupture specimens of this steel are analyzed via microhardness measurement, metallographic structure observation, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The results show that the matrix structure of the steel was stable during high-temperature stress-rupture test without grain growth. Twin boundaries in austenite gradually disappeared with the prolongation of time, which process was accelerated at higher temperatures. The steel hardness sharply increased in the initial stage of high-temperature stress-rupture test due to the second-phase precipitation, and then gradually dropped with time, due to the coarsening of precipitates. The Cu-rich phase and secondary Nb(C,N) with the size less than 50 nm, and M23C6 were the main precipitated phases in the high-temperature stress-rupture test. This allowed the steel under study to retain a high stress-rupture limit due to the precipitation-strengthening effect. The microstructure aging resulted in the formation of M23C6 chain at the grain boundary and coarsening of M23C6 and primary Nb(C,N) in grains. With the coarsening of precipitated phases, hardness and stress-rupture limit of Super304H stainless steel decreased.

Stress Rupture Properties of Welded Joints of Austenitic Heat-resistant Super304H Steel at 650 °C

With the help of metalloscope, scanning electron microscope and its energy dispersive spectroscopy, this paper investigates the stress rupture properties at high temperature and microstructure changes of the welded joints of austenitic heat-resistant Super304H steel at 650 °C as well as the effects of microstructure changes on stress rupture properties by high temperature creep rupture testing. The results show that at 650 °C, the welded joint of Super304H steel has high breaking strength at elevated temperature, and the fracture position is on the base material away from the fusion line, and the fracture type is mainly a transcrystalline rupture. The microscopic process of creep rupture of Super304H steel welded joints is the nucleation and growth of the void and crack, while the large bulk Nb(C,N) is the main nucleation site of void. As the careep time increases, M23C6 on the grain boundary is also the main nucleation site of the void.

Creep rupture strength of F12 steel welded joint after long-term service

Creep rupture strength of F12 steel welded joint which was used as the main steam pipe and serviced 165000 hours was investigated by using high temperature creep rupture testing. Microstructure analysis results show that the microstructure of F12 steel welded joint became embrittlement significantly after long-term service. The precipitates mainly consist of M23C6 carbide and Laves phase, and the amount of M23C6 phase is more, which precipitated along the grain boundaries in bulk or chainlike with larger size. At the same time, there are larger inclusions with directional distribution, in which these inclusions have poor bonding with substrate and easily become crack source during the process of high temperature creep. The high temperature enduring strength of welded joint of F12 steel decreased significantly, it is necessary to enhance the examination of the microstructure and life assessment of pipeline in the next overhaul period.

Effect of Ru on the concentration distribution of elements and creep properties of nickel-based superalloy

The effects of Ru on creep properties, microstructure and elemental concentration distribution of nickel..based single crystal superalloy containing without Ru and 2% Ru are studied by means of creep tests under high temperature, morphology observation after heat treatment and determination of elemental concentration distribution by atomic probe. The results show that Ru can inhibit the precipitation of TCP phase and improve the solid solubility of W element in the alloy and the creep life of the alloy at high temperature. At the same time, the addition of element Ru can make the alloy to produce “reverse distribution” effect, improve the alloying degree of γ’S phase and the effect of solution strength, which final significantly improve the high temperature creep rupture properties of the alloy containing Ru.

A new approach to predict creep rupture of Grade 92 steel under multiaxial stress states

The extension of the available stress-based predictive models from uniaxial to multiaxial feature is uncertain due to the difficulty to justify the model transferability to the cases which involves complex deformation and fracture mechanisms. This paper presents a new approach to predict the creep rupture life of Grade 92 steel under multiaxial stress state as the case of notched bar samples using Kachanov's Continuum Damage Mechanics (CDM) model. Combining the CDM model with the concept of Hayhurst's representative stress and accounting two extreme conditions; fully dislocation-controlled and diffusion-controlled creep mechanisms provide the bounds for short- and long-term rupture data of notched bar up to 10,000 h. Although the CDM is scientifically relevant and fundamental in their approach, it is generally complex and contains too many variables. Therefore, it needs proper measurements or numerically intensive to make the model acceptable for industrial applications. Alternatively, the recent developed strain-based exponential-type predictive model which links globally uniform failure strain with a multiaxial constraint factor was employed with the intention to reduce the large number of CDM parameters. The approach is relatively simple yet reliable to be used for high temperature creep rupture assessment.

Research on Remaining Life Evaluation Method of T92 Steel for Superheater Tube Based on Oxide Layer Growth

T92 steel is widely used in high-temperature superheater of supercritical power station boiler, and the researches on its remaining life have always been the hot spot of scholars around the world. In this paper, based on the analysis of high-temperature creep rupture strength data, the optimum C value of Larson–Miller parameter formula for T92 steel is obtained by using isothermal extrapolation method. On this basis, combining the relationship between the thickness of the oxide layer and the operating time, the relationship between the thickness of the oxide layer and the temperature of the tube wall and the relationship between the thickness of the oxide layer and the stress of the tube wall, a new remaining life evaluation formula is deduced. Finally, based on the cumulative creep damage life evaluation method, the service life of superheater tube is divided into three stages, which provides a new reference for the service life evaluation of superheater tube of ultra-supercritical boiler.