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1.
Inconel 718 is a frequently used material for gas turbine applications at temperatures up to 650 °C. The main load cycle for such components is typically defined by the start-up and shut-down of the engine. It generally includes hold times at high temperatures, which have been found to have a potential for greatly increasing the fatigue crack growth rate with respect to the number of load cycles. However, these effects may be totally or partly cancelled by other load features, such as overloads or blocks of continuous cyclic loading, and the actual crack propagation rate will therefore depend on the totality of features encompassed by the load cycle. It has previously been shown that the increased crack growth rate found in hold time experiments can be associated with a damage evolution, where the latter is not only responsible for the rapid intergranular crack propagation during the actual hold times, but also for the increased crack growth during the load reversals. In this paper, modelling of the hold time fatigue crack growth behaviour of Inconel 718 has been carried out, using the concept of a damaged zone as the basis for the treatment. With this conceptually simple and partly novel approach, it is shown that good agreement with experimental results can be found. 相似文献
2.
Replica-based crack inspection 总被引：1，自引：0，他引：1
John A. Newman Scott A. Willard Robert S. Piascik 《Engineering Fracture Mechanics》2009,76(7):898-910
Surface replication has been proposed as a method for crack detection in space-shuttle main engine flowliner slots. The results of a feasibility study show that examination of surface replicas with a scanning electron microscope can result in the detection of cracks as small as 0.005 inch, and surface flaws as small as 0.001 inch, for the flowliner material. 相似文献
3.
高温合金中的溶质晶界偏聚是影响合金多方面性能的重要因素.以高温合金Inconel 600和Inconel718为研究对象,总结了合金中溶质晶界偏聚的研究现状,并对已有的研究成果进行了深入分析,结果发现:溶质在Inconel 600合金中的偏聚规律对舍金性能的影响还需要进一步研究晶界偏聚特性、基本物理参量以及晶间腐蚀抗力的作用;溶质在Inconel 718合金中的晶界偏聚对合金性能的影响依然有待于进一步研究其作用机理、偏聚动力学和共偏聚特性.同时,指出今后高温合金中溶质晶界偏聚的研究方向为溶质晶界偏聚动力学以及溶质问晶界共偏聚行为. 相似文献
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对从Inconel718合金管材截取的O形环小试样进行了压缩回弹试验研究.试验表明,温度、加载历史和轴向尺寸对O形环回弹量无明显影响;常温下O形环回弹量随压扁度的变化在6%~30%的压扁度范围内表现为抛物递增,此时O形环密封性能良好,但当压扁度超过30%,回弹量开始递减,且试样的压缩接触面伴随出现凹陷,在600℃以上还发生坍塌.运用ANSYS的弹塑性接触分析功能,采用不同的本构模型,分别建立了二维、三维有限元网格模型,对O形环的压缩回弹过程进行了数值模拟.研究表明,ANSYS的弹塑性接触有限元方法对O形环回弹量的分析模拟结果与试验结果吻合较好. 相似文献
6.
Confined crack tip plasticity model is employed to predict time independent fatigue crack growth rate (FCGR) behavior of HAYNES® 282® alloy at temperatures 1200F and 1400F. Crack growth tests were done in lab air, vacuum and steam environments at load ratios R = Kmin/Kmax ranging from 0.05 to 0.5. Calibrated model predicts average cyclic crack growth rate behavior of the material reasonably well. Predictions do not capture the accelerated fatigue crack growth rates observed in the data at low load levels. Such effects are believed to be caused by environmentally driven factors, which are not expected to be predicted by plasticity based models. 相似文献
7.
《Materials and Manufacturing Processes》2012,27(10):1066-1072
It has been observed that considerable attention has been given to the use of cBN and/or ceramic tools for achieving better performance in the machining of superalloy Inconel 718. However, their cost limits the use in the engineering applications. In this article, the performance of multicoated TiN/TiAlN (PVD) coated and TiN/Al2O3/TiCN (CVD) coated tungsten carbide tools were investigated while high speed turning (HST) of superalloy Inconel 718. The effect of coating materials on cutting force, cutting temperature, vibration, and acoustic emission were recorded, analyzed, and reported. From the experimental results it has been found that TiN/Al2O3/TiCN (CVD) coated tool outperformed the TiN/TiAlN (PVD) coated tool in terms of machinability parameters such as cutting force and cutting temperature. From the fast Fourier transform (FFT) analysis of the vibration signals it was observed that the vibrations were less in case of the CVD coated tool than in case of the PVD coated tool. 相似文献
8.
The effect of δ phase on the hydrogen embrittlement (HE) sensitivity of Inconel 718 was investigated by conducting notch tensile tests. Notch tensile specimens with various precipitation morphologies of δ phase were prepared with different heat treatments, and hydrogen was charged into the tensile specimens before tensile tests via a cathodic charging process. The loss of notch tensile strength (NTS) due to the charged hydrogen was used to evaluate the hydrogen embrittlement sensitivity. The results show that δ phase has deleterious effect on NTSs, and the fracture of hydrogen-charged specimens initiated near the notch surfaces. The loss of NTS caused by precharged hydrogen can be greatly decreased by dissolving δ phase. δ-free Inconel 718 alloy is proposed for the applications in hydrogen environments. 相似文献
9.
《Materials and Manufacturing Processes》2012,27(11-12):1410-1416
Drilling of small-diameter holes meeting stringent quality standards in superalloys such as Inconel718 (having widespread applications in aeroengine component manufacturing) has always been a challenging task. Laser drilling has wide applications in the aerospace industry. Laser trepan drilling (LTD) provides better control over the drilled hole geometry compared with laser percussion drilling to fulfill the higher dimensional accuracy requirement. This article presents an integrated approach of artificial neural network and genetic algorithm for the modeling and optimization of geometrical quality characteristics such as hole taper and circularity during LTD of 1.6 mm thick Inconel718 superalloy sheet. The optimum results show considerable improvements in hole taper, and hole circularities at laser beam entry and exit sides. Higher values of laser pulse frequency and trepanning speed in the present range have resulted in more circular holes with reduced taper. 相似文献
10.
《材料与设计》2015
Nickel-base superalloys are used in highly demanding applications such as energy and aerospace industries. These alloys present good corrosion resistance, weldability and mechanical stability at high temperatures. Numerical methods are commonly used to predict the mechanical and microstructural behavior of heat resistant alloys. The aim of the present work was to model recrystallized grain size evolution under isothermal conditions using the cellular automata (CA) technique. The CA model was applied to simulate hot compression of Inconel 718 nickel-base alloy at 980 °C and 1020 °C. A finite element analysis was conducted to acquire input parameters to the model such as strain and strain rate. Hardening and recovery coefficients were calculated in order to represent the competitive effects during deformation. The influence of local changes of initial grain with fully and partial recrystallized microstructures were simulated by CA and compared with isothermal hot compression results. The model was able to comprehensively predict necklace type microstructures. The average grain size was generally in good agreement with the experimental data. 相似文献
11.
Growth of long fatigue cracks is investigated in Inconel 718 superalloy produced by selective laser melting (SLM). The fatigue crack growth curve and the threshold value of the stress intensity factor are experimentally determined on compact-tension specimens fabricated using a RENISHAW A250 system and the recommended processing parameters.The crack propagation curve and the crack propagation threshold of this SLM material are compared with literature data describing the behavior of conventionally manufactured Inconel 718. The fatigue crack growth is discussed in terms of the specific microstructure and residual stresses produced by selective laser melting. 相似文献
12.
Crack growth in MA 6000 under cyclic loading was studied at 24, 760, and 1000°C and under static loading at 1000°C in two matenal onentatwns. Correlatwns of fattgue crack growth rate with parameters ?K and ?J were examined. Also comparisons were made of experimental and predicted growth rates.The rate of growth was influenced by temperature and onentatwn m addttwn to the loading mode. Fatigue crack growth rate generally increased with temperature. However in the L-T orientation at 1000°C secondary cracks developed perpendtcular to the primary crack and significantly altered its behaviour. Creep crack growth at 1000°C was strongly orientation dependent, mainly due to secondary crackmg m the L-T oriented specimen in the direction perpendicular to the main crack.Fracture surfaces were examined by scanning electron microscopy. Also, comparisons were made between crack growth behaviour of MA 6000, MA 754 and MA 956. 相似文献
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Peeyush Nandwana Michael Kirka Alfred Okello Ryan Dehoff 《Materials Science & Technology》2018,34(5):612-619
ABSTRACTThis study reports the effect of process temperature on microstructure evolution of electron beam melted Inconel 718. Samples fabricated at 915°C had fine grain boundary δ (～200?nm) along with coarse intragranular δ spanning through the length of the grains. On the other hand, samples fabricated at 990°C, only had grain boundary δ along with secondary carbides. During hot isostatic pressing, the distribution of carbides governs the grain growth vs. lack of it. The samples fabricated at 990°C having grain boundary carbides had no grain growth owing to the pinning effect of carbides. In contrast, the sample processed at 915°C had significant grain growth owing to dissolution of grain boundary δ phase and absence of grain boundary carbides. 相似文献
15.
Inconel 718 superalloy has wide applications in several industries due to its excellent mechanical properties. However, it is very difficult to machine using conventional cutting and grinding because of its high strength at elevated temperatures. Electrical discharge machining (EDM) is an alternative competitive process to machine Inconel alloys by electrical erosion. However, machinability and surface characteristics of EDMed Inconel surfaces are poorly understood. This study focuses on the machining characteristics of Inconel 718 by Wire-EDM and Sinking-EDM with a new Cu-SiC electrode, respectively. Material removal efficiency, surface roughness, surface topography, surface alloying, and electrode wear have been characterized. It is found that the high toughness of Inconel 718 would be the major contributing factor to the absence of microcracks on the EDMed surface. The new fabricated Cu-SiC electrode for Sinking-EDM has better performance in terms of material removal rate (MRR), surface roughness, and electrode wear. The higher melting temperature and fine microstructure of SiC contribute to the lower electrode wear of the new Cu-SiC electrode than the traditional Cu electrode. 相似文献
16.
The microstructural evolution of Inconel 718 during aging processes has been studied through a combination of eddy current testing, X-ray diffraction analysis, and metallography and hardness measurements. Measurements were carried out in samples subjected to eight different heat treatment cycles, between 620 and 1035°C for 1–18 h. Different amounts of secondary precipitates were achieved, reaching 18% of delta phase for samples overaged at 900°C for 18 h. Results show that the different microstructures of Inconel 718 obtained have a distinguishable effect on electrical conductivity when this is measured through an appropriately sensitive technique (i.e. eddy current testing). The lowest conductivity values were observed for under aged samples (1·44% IACS). A clear increase in conductivity values was seen for all aged or overaged conditions, reaching a maximum of 1·63% IACS, when coarsening of intra granular precipitates, associated with an increase in density of globular precipitates at grain boundaries, was identified. The influence of microstructure on conductivity could be shown to be due to the competition between two effects on the scattering of electrons: matrix purification and precipitation characteristics. A combination of hardness values and electrical properties proved to be a fast and practical way of determining the stage of aging of the alloy. 相似文献
17.
《Materials and Manufacturing Processes》2012,27(3):337-343
Inconel718 superalloy is one of the difficult-to-cut materials used widely in the aerospace industries. Inducing high tensile residual stress is a critical problem during the machining of Inconel718. This problem becomes more detrimental in presence of rough machined surface because fatigue life of the manufactured components might be decreased significantly. The aim of the present study is to access desired machining parameters including cutting speed, depth of cut, and feed rate for simultaneous optimizing surface roughness and tensile residual stress in the finish turning of Inconel718. After conducting experimental measurements, the results were introduced to the artificial neural networks. Then, the functions implemented by neural networks were defined as objective functions of nondominated sorting genetic algorithm. Finally, it was shown that implemented hybrid technique provides a robust framework for machining of Inconel718 superalloy. 相似文献
18.
The effect of δ phase on the hydrogen embrittlement (HE) sensitivity of Inconel 718 was investigated by conducting notch tensile tests. Notch tensile specimens with various precipitation morphologies of δ phase were prepared with different heat treatments, and hydrogen was charged into the tensile specimens before tensile tests via a cathodic charging process. The loss of notch tensile strength (NTS) due to the charged hydrogen was used to evaluate the hydrogen embrittlement sensitivity. The results show that δ phase has deleterious effect on NTSs, and the fracture of hydrogen-charged specimens initiated near the notch surfaces. The loss of NTS caused by precharged hydrogen can be greatly decreased by dissolving δ phase. δ-free Inconel 718 alloy is proposed for the applications in hydrogen environments. 相似文献
19.
The steady state creep rate equdtion ofa nickel base superalloy Inconel 718, strengthenedby coherent ordered disc-shaped bct γ~(11) phaseand coherent spherical fcc γ~1 phase precipitates,has been established in the stress and temperatureranges of 620-840 MN m~(-2) and 853-943K, respecti-vely. Constant stress tensile creep tests wereused to medsure the values of steady state creeprate, ε_s, and the consecutive stress reductionmethod was used to measure the back stress duringcreep deformation. The values of effective stressexponent, n_e, were detemined from the slopesof the lgε_s vs. lg(σ_a-σ_0)/G plots. The effectof grain size, d, on steady state creep rdtehas been also studied in this investigation,and the grain size sensitive exponents m weredetemined from the slopes of lgε_s vs. lg(b/d)plots. The creep rate equations of Inconel 718,in the above stress and temperature ranges,have been proposed to beε_s=1.6×10~(-5)(D_1Gb/KT) (b/d )~(0.19)[(σ_a-σ_0)/G]~(1.35)in diffusional creep region, andε_s =75(D_1Gb/KT) (b/d)~(-0.42)[(σ_a-σ_0)/G]~(5.5)in dislocation power law creep region. 相似文献
20.
《材料科学技术学报》2024,202(35)
To provide insight into the effect of grain size on the precipitation behavior of γ\"strengthening super-alloy Inconel 718,a gradient nanostructure with a large grain size span(from 9 nm to tens of microns)along the depth direction was achieved by mean of surface mechanical grinding treatment,followed by annealing upon 700-1000 ℃ for 1 h.The results reveal significant differences in the type and size of precipitates in samples with different grain sizes.No y\"precipitate was detected inside the grains as the grain size was refined down to 40 nm(NG-40)and 9 nm(NG-9).For δ phase,a significantly accelerated precipitation along grain boundary was observed in NG-40 upon 700 ℃ annealing.Interestingly,with the grain size drops to 9 nm,the precipitation of δ was suppressed,with some nanosized MC carbides appearing upon annealing.The grain size effect of precipitation behavior endows NG-9 an ultra-high RT-hardness(5.2 GPa)after 1000 ℃ thermal exposure and an ultra-high hot-hardness(3.2 GPa)at 800 ℃. 相似文献