Energy Materials 2017

In China, many technologies have been applied to improve the energy efficiency of the processes. Among these technologies, the waste energy recovery technology, for example, CDQ (coke dry quenching), CCPP (combined cycle power plant), waste energy recovery from Linz-Donawitz process, etc. have been used widely and contributed a lot to the energy savings whose application status and energy recovery effect assessment were analyzed in this paper. Further, the technologies of the next generation, aiming to recover the low-grade waste heat, are under development considering the exergy efficiency principle with novel energy conversion methods. Two typical processes under development which are the vertical tankVertical tank cooling system for sinter sensible heatSinter sensible heat recovery and the Organic Rankine CycleOrganic Rankine Cycle (ORC) system to recover the waste heat from blast furnace (BF) slag quenching water for power generation were introduced and their significance and the feasibility were analyzed.

Shougang Jingtang Steel Plant is the project which is built based on the concept of new generation recycling iron and steel process, with characteristics of “three functions”, namely iron and steel product manufacture, high efficient conversion of energy, and disposal of wastes by reutilization. In engineering designEngineering design, on the strength of theory of metallurgical process engineering, the advanced iron and steel manufacturing process of static process structure has been established by construction of two blast furnaces, one steel making plant and two hot rolling production lines, the advanced interface technology on ironmaking and steelmaking process has been developed, and the complete process of energy flow networking framing technology has been created. Energy consumption is reduced, with sufficient recovery of gas, heat and surplus energy during iron and steel manufacturing process, as well as emission reduction of dust and pollutant so as to achieve green iron and steelGreen iron and steel manufacturing and recycling economy, and energy utilization efficiency has an outstanding improvement. This paper introduces the green iron and steel manufacturing process of Shougang Jingtang Iron & Steel Plant, and establishment of its energy flow network.

In order to reduce the energy consumption from iron and steel industry, decreasing coke rate by establishing oxygen blast furnaceOxygen blast furnace (OBF) ironmaking process is a favorable way. In recent years, many scholars and metallurgical workers from all over the world have made a lot of related work about this ironmaking process. The main content in this paper is as follows: The necessity, process characteristics and optimization research of OBF were introduced. The optimal OBF process were elected by the calculation of energy-mass balance mathematical model. In order to cope with the subsequent industrial test, theoretical calculation of the improved process is carried out. The process parameters under different oxygen enrichment rateOxygen enrichment rate 9, 19, 29%, and eventually reached 100% are calculated. Calculation results show that with the increase of oxygen enrichment rate, the recycling gas volume from both shaft tuyere and hearth tuyere were increased, the coke rate gradually is reduced and the coal rate increased gradually. After adopting the OBF ironmaking process the ironmaking costs and CO₂ emissions can be greatly reduced.

Byproduct gasesByproduct gases generated during the iron and steelIron and steel industry making process are important energy sources in steel plant, which accounted for 30% of total energy consumption. With the increasing need for production cost control in steel industry, the refined management of byproduct gases has become prominent. The predictionPrediction and optimal schedulingScheduling of byproduct gases are two key factors in the optimal management of byproduct gases. However, due to the complexity and dispersivity of byproduct gas generation and consumption, it is difficult to build a comprehensive and reasonable prediction and scheduling model. This paper reviews current methods in the prediction and scheduling of byproduct gas system and discusses some of the key factors and opportunities in improving the model. Emerging trends that are likely to influence the current or future byproduct gas prediction and scheduling are also discussed.

Obtaining the ideal {001}⊥ND textureTexture in non-oriented electrical steelNon-oriented electrical steel sheets was the goal of many past investigations. However, it was difficult to achieve the desired texture using conventional rollingRolling techniques since the metallurgical mechanisms governing the thermomechanical processing usually promote the formation of the undesired {111}⊥ND texture. In this research, two unconventional cold rolling schemes were proposed and tested: (i) inclined rolling, in which the cold rolling direction (CRD) was inclined at an angle (0°–90°) to the hot rolling direction (HRD) so that the initial texture was changed; (ii) skew rolling, in which the hot band was fed into the rolls at an angle (0°–45°) to the conventional feeding direction so that both the starting texture and the rolling deformation were changed. Non-oriented electrical steels containing 0.9 and 2.8 wt%Si were cold rolled using these schemes, and the textures were measured. It was found that both schemes have considerable effects on the deformation and recrystallizationRecrystallization textures. Finite elementFinite element methods simulations of the skew rolling process were performed to illustrate the stress/strain imposed on the material, which revealed a fundamentally different deformation mode from plane-strain rolling.

The integrated systemSystem integration of smelting reduction ironmakingSmelting reduction ironmaking—gasoline synthesisGasoline synthesis—electricity generationElectricity generation was simulated by computer, in which the surplus coal gas produced in ironmaking is cleaned and used as the fuel of electricity generation or raw material of gasoline synthesis. The system can settle the problem of the utilization of tail gas in the smelting reduction ironmaking and the large investment of gasification in the integrated gasification combined cycle and gasoline synthesis. Taken efficiency, scale and product structure into consideration, the processProcess simulation of two-stage smelting reduction ironmaking—combined cycle electricity generation with coal gas, the process of two-stage smelting reduction ironmaking—steam cycle electricity generation with coal gas, the process of one-stage smelting reduction ironmaking—combined cycle electricity generation with coal gas and the process of one-stage smelting reduction ironmaking—gasoline synthesis with coal gas—steam cycle electricity generation with tail gas may be industrialized.

During the casting of ferromanganese alloys, a considerable amount of dark fumes, consisting primarily of manganese oxides, are generated when the Mn vapour oxidises in the atmosphere. Previous studies indicate that these fumes can be reduced by increasing the humidity above the melt. However, the reduction mechanism is not fully understood. In an attempt to understand the reduction mechanism, the influence of a humidity change on the fuming rate was studied. Laboratory scale experiments were conducted where an impinging jet blew air with a varying humidity onto the melt where dust was captured to determine relative mass fluxes. When the wet air experiments’ fume fluxes were compared to the dry air experiment, it was found that the increase in humidity resulted in a significant fume reduction (between 33 and 79%), confirming industrial observations. Dust composition from the experiments as well as dust reduction mechanisms are presented and discussed.

Within the scope of the Advanced Metals and Processes (AMAP) research cluster in Aachen (Germany) the aluminium recyclingAluminium recycling process in melting furnaces is investigated with regard to resource and energy efficiency. When organic-contaminated material is charged into the furnace, pyrolysis gasesPyrolysis gases are released as soon as the material temperature exceeds approximately 350 °C (662 °F). Those gases mainly consist of hydrocarbons, hydrogen and small fractions of other species. Thus, they are an energetic contribution to the furnace atmosphere and should be considered as such by the burner control unit in order to reduce the amount of unburnt fuel in the off-gas as well as primary energy consumption. This is achieved by post-processing data from lab-scale pyrolysis experiments in MatLab and bringing it into a format suitable for computational fluid dynamics (CFD) simulations. In this article an insight into the modelling approach and the model application in ANSYS Fluent CFD is given.

Within the scope of the project P5 of the AMAP (Advanced Metals And Processes) research cluster in Aachen a virtual remelting furnace is set up as a CFD (Computational Fluid Dynamics) simulationCFD simulation to investigate the resource and energy efficiency of the aluminium recyclingAluminium recycling process in melting furnaces. During the melting process of aluminium scrap (e.g. used beverage cans) a reactive flow has got a major impact on the heat transfer to the load. Thereby it is mostly dominated by gas combustionCombustion due to the heating burners in the furnace and pyrolysis/thermolysis reaction caused by organic contamination of the charge. Obtaining more understanding of the underlying mechanisms is imperative for improving the performance of the melting and combustion process and in preservation of the equipment. In the present work, numerical simulations were carried out using the commercial software FLUENT for generating a helpful tool in evaluating operational conditions. The main perspective is to analyse the relevant operational conditions inside an aluminium melting furnace employing methane oxygen burner which is capable to run in the flameless combustionFlameless combustion mode. To overcome the obstacle of simulating highly diluted combustion occurrence proved detailed chemistry model is involved. Another important aspect is to evaluate additional in house written codes for the evaporation and gas release due to contaminated input material. The subject of the investigation is the numerical simulation of the heating and holding process sequence as a steady state process.

Low-grade waste heat from industrial processes usually has temperatures lower than ~232 °C, and thus has low thermal and economic values. However, low-grade waste heat is abundant and its total work potential is huge. To effectively recover low-temperature waste heat, i.e. recover both the sensible and latent heats, the exhaust streams usually need to be cooled to temperatures below the water and acid dew points, which causes severe corrosionCorrosion problems in the heat exchangers. In this research, a fluoropolymerFluoropolymer-based composite coatingCoating was applied to heat exchangers made of inexpensive metals (e.g. stainless steel, aluminum, carbon steel, etc.) to protect the surfaces contacting the waste streams. Corrosion tests were conducted in 80% sulphuric acid at ambient and elevated temperatures for more than 1500 h, and no corrosion was detected. The composite material has much higher thermal conductivity than virgin fluoropolymerFluoropolymer, and can be applied to both bare and finned heat exchangers. The composite coating can be continuously utilized at temperatures up to ~260 °C. The coating also shows excellent adhesion strength to the substrate.

NitrateNitrate contamination is a water pollution problem in the U.S. and globally. Mining and agriculture disperse nitrate into water supplies creating significant contamination in receiving waters. There is increased demand for new water technologies to meet new regulations and more exacting effluent standards. Standard chemical/physical water treatment technologies do little to aid in meeting effluent standards for nitrate and associated anionsAnions such as selenateSelenate and sulfateSulfate. The Winner Water HydroFlexHydroFlexTM system is an adaptable technology to remove nitrate, selenate and sulfate from waste water. HydroFlex includes solvent extractionSolvent extraction loading, scrubbing and stripping with a strong base anion exchange solvent. Nitrate may be stripped as a strong solution of calcium nitrate using a milk of lime strip solution. The loading and stripping data from testing of HydroFlex on a wastewater sample will be presented and discussed along with an economic model demonstrating the cost effectiveness of the technology.

In the iron making process of blast furnaceBlast furnace, the size and location of racewayRaceway have an important impact on the distribution of gas flow and gas/solid temperature. Based on a one-dimensional cold-state model, the similar geometry model, subarea method and basic force model were employed in this article to derive and accurately calculate the forces of gravity, gas pressure and friction. Combining a three-dimensional cold-state experimentExperiment of raceway detection with optical method, a new expression of raceway size with the blast velocity was obtained as well as the modification factor of gas pressure.

To meet the requirements of 700 °C ultra-supercritical (USC700 °C USC) coal-fired power plants, a new Ni-Fe based alloy (GH984G) has been developed. GH984G has excellent creep strength, thermal stabilityThermal stability and resistance to oxidation/corrosion. Harmful phases were not observed even if after thermal exposure at 650–750 °C for 35,000 h. After exposure at 700 °C for 30,000 h, the yield strength has no obvious change. Its 105 h creep strength at 700 °C is up to 137 MPa and comparable to the level of 617B. The oxidation/corrosion evaluate at 700–800 °C up to 2000 h shows that it can meet the requirements of 700 °C USC coal-fired power plants. Currently, the pipesPipe and tubes with different sizes have been manufactured. Moreover, it is an economic alloy due to the elimination of Co and containing more than 20% Fe. This makes it an interesting alternative for 700 °C USC coal-fired power plants and is now being evaluated at test platform for key components of China.

G115 is a novel ferritic heat resistant steels developed by CISRI in the past decade, which is an impressive candidate material to make tubes, pipes and forgings of advanced ultra super critical (A-USC) fossil fired power plants used for the temperature scope from 600 to 650 °C. The successful development of G115 extends the upper application temperature limitation of martensitic steel from 600 °C to about 650 °C. This breakthrough is imperative for the design and construction of 610 to 650 °C A-USC fossil fired power plants, from the viewpoint of the material availability and economics of designed coal fired power plants. This paper introduced the creep strengthCreep strength and oxidation resistanceOxidation resistance of industrially made G115 steel pipeG115 steel pipe, including the experimental phenomenon description and theoretical mechanism explanation.

Conventional “constant-load” creep tests of new steels for thermal power generation and chemical processing are very long lasting, thus delay application of new steels for years. Same problem appears with creep tests on heat-affected zones in welded joints of these steels, as welding procedure influences their properties. And frequent power plant shut-downs due to adding solar/wind power to the net, call for creep-fatigue data which standard creep tests cannot provide. To address all these issues a test was developed allowing to obtain creep life data in less than 24 h. The accelerated creep test is a low-cycle thermal-mechanical fatigue procedure based on detailed microstructure study of crept steels and welds. It is carried-out on Gleeble physical simulator. The paper explains selected ACT results and describes microstructures.

12Cr1MoVG is a pearlite heat-resistant steel of the standard GB5310 “seamless steel of high pressure boiler”. In this paper, the latest application progress for ASME code case of 12Cr1MoVG steel12Cr1MoVG steel is introduced. As steels used for the USC boilerUSC boilerwater wallWater wall, properties and operation reliability of 12Cr1MoVG and T23 are compared. When 12Cr1MoVG instead of T23 is chosen to manufacture the USC boiler water wall, it will increase the operation reliability; decrease the raw material cost as well as the difficulty of manufacture and installation.

The effect of high-frequency induction hardeningHigh-frequency induction hardening on stress corrosionStress corrosion of a 12%Cr martensitic stainless steel12% Cr martensitic stainless steel in 22%NaCl solution was investigated by stress corrosion test. The stress corrosion properties of quenched-and-tempered zone and high-frequency hardening zone were analyzed by an electrochemical workstation and compared with each other. The microstructure, phases and stress corrosion fracture were studied by optical microscopy, transmission electron microscopy and scanning electron microscopy. The test results show that the pittingPitting tendency of high-frequency hardening zone is smaller than that of the quenched-and-tempered zone. The cracks initiate at the bottom of surface pits and propagate by an intergranular mode in quenched-and-tempered zone. The microstructure of quenched-and-tempered zone are tempered sorbite. Many (Fe, Cr)7C3, (Fe, Cr)23C6 carbides of this zone are prone to segregating on dislocations in the lath cell walls of martensite laths and cell boundaries, which leads to local Cr depletion. The microstructure of high-frequency induction hardening zone was tempered martensite with little (Fe, Cr)3C and (Fe, Cr)7C3 carbides.

Fireside corrosionCorrosion behavior of Inconel 740HInconel 740H superalloy was studied at 750 °C in simulated coal ash/flue gasCoal-ash/flue-gas environments by means of XRD, SEM and EDS. The results indicated that the corrosion behavior was strongly related to the SO₂ levels and was significantly affected by NaCl additions. In presence of the atmospheres with 0.1%SO₂, the alloy exhibited the highest corrosion resistance due to formation of a stable and dense Cr₂O₃ film. In present of the atmosphere with 1.5%SO₂, however, a non-coherent and porous Cr₂O₃ film was formed. The thickness of film and internal sulfides were substantially increased. The mechanism of ash corrosion formation was also discussed.

The high cycle fatigueHigh cycle fatigue performance tests for nickel-based alloy HAYNES282 at room temperature, 700 and 760 °C had been carried out. The optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the change features of microstructureStructure and fracture. The results shows that the precipitation of γ′ phase which makes alloy has excellent high cycle fatigue performance is a guarantee of high strength of the alloy, and fatigue strengthFatigue strength reduces slowly with the temperature increasing. The fracturing pattern was in monophyletic fatigue source, and extended in the form of cleavage and quasi cleavage and had obvious river pattern characteristics. At the same time, the fatigue cracks propagate in the form of dislocation slip, and the coarsening of γ′ hinder the dislocation sliding and climbing as the temperature rise, which improved the fatigue strength of the alloy.

Raising the operating temperature and pressure of the steam turbine can improve the thermal efficiency in order to reduce the fossil fuel consuming and CO₂ emissions. Alloy 625 is a solution strengthened Ni-base superalloy and has been considered as one possible candidate for A-USC steam turbine castings. In this research, we investigate the chemical composition, microstructure, tensile and creep behavior, and long-term thermal stability of an Alloy 625 step block, which was produced by sand casting. Nb segregation has been observed in the thick section. Segregation can influence the mechanical properties and cause defects in large casings and valves. The alloy exhibits excellent creep properties and thermal stability, however, the ductility of Alloy 625 casting decreased significantly after 1000 h at 700 °C. Alloy 625 can meet the design requirements of A-USC steam turbine, but also need further research on the production process.

One impact of the reaction of thermal barrier coatings (TBCs) in gas turbine engines with volcanic ash or other debris (CMASCMAS) is a change in the thermal conductivityThermal conductivity. In this study, the effective thermal conductivity of the potential TBC material Sm₂Zr₂O_7Sm2Zr2O7 was determined after CMAS reaction below and above the melting temperature of the CMAS. The conductivities of Sm₂Zr₂O₇, CMAS, and the reaction layer were determined separately. The phase content and microstructure were characterized with scanning electron microscopy and X-ray diffraction. The change in microstructure and formation of Ca₂Sm₈(SiO₄)₆O₂ led to an increase in the effective conductivity, which would reduce the effectiveness of the TBC.

Based on the principle of superalloy design, seven alloy compositions for heavy IGTHeavy IGT (Industry Gas Turbine) blades application were designed to meet the’ demand for alloy’s properties, like stress rupture, hot corrosion resistanceHot corrosion resistance, stability of microstructureStability of microstructure, etc. Through thermodynamic equilibrium phase calculation and electron vacancy number calculation of Woodyatt method, three kinds of test alloys were studied as primary selections. After testing of mechanical propertiesMechanical properties, hot corrosion resistance etc., a new kind of hot resistant directionally solidified superalloyDirectionally solidified superalloy DZ409 with high strength, outstanding hot corrosion resistance and microstructure stability properties, was developed for the manufacturing of heavy IGT blades.

As demands of energy supply have been increased continuously and at the same time the uses of fossil fuel are limited and the greenhouse effect should be minimized, the gas turbine industries have been making efforts to increase gas turbine efficiency and to reduce emissions for power generations. One of the efforts is a continuous development of high temperature capacity of ceramic thermal barrier coatings (TBCs) and metallic MCrAlYMCrAlY overlays. The MCrAlY overlays are used as both protective coatings and bond coats to TBCs on underlying superalloy components in the gas turbines. During high temperature exposure, elemental diffusion occurs between the bond coat and the substrate which can affect the overall coating performance. The present study investigates the diffusion of minor elementsMinor Elements like Re, Ta, Si, Mo and Ti in various MCrAlY overlays and superalloy substrates. An oxidation-diffusion model has been used to study the elemental diffusion. The diffusion process contains two stages: β depletion stage and the β depleted stage. In the stage when MCrAlY overlays exhibit γ + β microstructure, the diffusion of minor elements in the coatings was observed to be related to the β depletion rate. After that the diffusion of the minor elements did not show any clear dependence on the coating composition. The development principle of the elemental diffusion is discussed in detail.

The purpose of this study is to evaluate the effects of hot isostatic pressingHot isostatic pressing (HIP) on the porosity healingPorosity healing and the microstructure evolutionMicrostructure evolution of a cast superalloyCast superalloy K452, which is generally applied for fabrication the vanes with the bigger size. The annihilation degree of the porosity, related to the location and shape of the porosity as well as HIP temperature, were studied by high resolution transmission X-ray tomography (HRTXRT) and finite element method (FEM). Results showed that the most of porosities (over 80%) were eliminated by HIP at 1200 °C, in which the porosity located in the thin walled parts and with the loose-flat shape was easy to be healed, and the diameter of remnant porosities was decreased to less than 10 μm. Accordingly, A healing mode of the porosity was established. Furthermore, It was found that the slow cooling rate during HIP would obviously lead γ′ precipitates to coarsen, while the rejuvenation heat-treatment (RHT) after HIP could reduce the dendritic segregation degree and readjust the coarsen γ′ precipitates, which finally improved the mechanical properties of the cast superalloy. The HIPed K452 alloy vanes have been successfully used in a civil gas turbine.

The effect of the dendritic segregation degree on volume fractions and nucleation sites of recrystallization was investigated through comparing three kinds of samples with heavy degree of dendritic segregation, with light degree of dendritic segregation and without the dendritic segregation. The degree of the dendritic segregation was controlled by altering homogenization time. Stress concentration was caused by uneven distributions of γ′ phases in dendrite armDendrite arm and interdendritic areasInterdendritic area. Meanwhile, recrystallization was retarded due to the pinning effect of γ′ phases in interdendritic areas. Thus, the recrystallization nucleationRecrystallization nucleation started along the grain boundary, then in the junction of dendrite arm and interdendritic areas but at the side of dendrite arm areas with the increase of the deformation degree. Finally, nucleation occurred in the interdendritic area. Moreover, strain concentration was released as γ′ phases were more evenly distributed with the increase of homogenization time which lead recrystallization volume fractions reduced with the decrease of dendritic segregation.

Alloy 783Alloy 783 because of its high temperature oxidation resistance, excellent mechanical properties and low thermal expansion coefficient, not only can be applied in aviation gap control component, can also be used in high temperature bolt USC Turbine serving. High temperature mechanical properties of the alloy, particularly the stress rupture properties is essential for the alloy can be used normally under severe conditions. The effects of different Al contents, stress and temperature on the alloy rupture lifeStress rupture life were tested by the method of orthogonal experimentOrthogonal experiment and analyze the main factors affecting the performance of the alloy.

The critical undercooling degree (ΔT_N) of nickel-based superalloysNickel-based superalloys has a great relationship with the single crystal castability. This paper studied the ΔT_N of DD483, CMSX-4 and CMSX-6, also analyzed the factors affecting ΔT_N, including chemical composition, shell materials and remelting cycle. The results show that when experiment condition of pouring temperature and shell materials remains the same, three kinds of superalloys have different undercoolabilityUndercoolability, and the order of the critical nucleation undercooling degree from high to low is CMSX-6, CMSX-4, DD483. Because of the influence of wettability between alloy melt and shell, ΔT_N of CMSX-4 in the pure Al₂O₃ shell is greater than which in EC95 shell (95% pure corundum + 5% quartz). With increasing the number of remelting, shell aging may pollute the alloy melt, leading to a decline in the undercoolability of the alloy.

The strain-controlled fatigue tests of cold-drawn 316 austenitic stainless steelsStainless steels used in nuclear reactors were conducted at room temperature. The fractography of the specimens after fatigue fracture was observed by scanning electron microscope. The interaction between mechanical twinsMechanical twins activated by prior cold drawingCold drawing and dislocation structures during fatigue of cold-drawn 316 steels was investigated by transmission electron microscope. The results reveal that the high-cycle fatigueHigh-cycle fatigue life of 316 stainless steels can be raised by prior cold drawing. The high-cycle fatigue life obviously increases with the level of prior cold drawing. The fatigue crack propagation rate of 316 stainless steels was decreased by the prior cold drawing. The complex dislocation structures, like walls, channels and cells, were generated during fatigue. The mechanical twins can segment the austenitic grains and hinder the dislocationsDislocations motion between two mechanical twins. The dislocations pile up and slip along the mechanical twin boundaries. The extrusion on austenitic grain boundaries resulting from dislocations motion can be reduced by mechanical twin boundaries, leading to effectively improve deformation homogeneity and delay fatigue micro-crack initiations. Also, the high-cycle fatigue resistance of cold-drawn 316 stainless steels can be improved by the grain refinement resulting from mechanical twins. Thus, the high-cycle fatigue property of 316 steels is enhanced through the mechanical twinsMechanical twins activated by cold drawing.

The electron microscopy techniques were employed to analyze the microstructure evolution during high-temperature tempering of a reactor pressure vessel steel. The results show that carbon enriched martensite/austenite (M/A) constituents decomposed into ferrite laths and accumulated carbides during initial stage of tempering. Simultaneously, the carbon atoms in the constituents diffused into the matrix continuously. With further prolonging of tempering, Mo₂C carbides were found to be distributed uniformly in bainitic ferrite. In case of longer tempering, bainitic ferrite would combine and broaden, and grain boundary carbides grew up sequentially and coarsened. The newly formed austenite was detected during tempering at 660 °C for 5 h, and at 650 °C for 100 h,which shown that the Ac₁ is time-related. This phenomenon may be depend on the component fluctuation of M/A constituents and segregation of carbides.

The Canadian Supercritical Water-cooled Reactors (SCWR), among the Generation IV (Gen IV) reactors concepts, are currently being developed in Canada and many other countries. The preliminary design of the Canadian SCWR uses a coolant operating under a pressure of 25 MPa at 625 °C, reaching a peak cladding temperature as high as 800 °C. This presents challenges in materials selections due to limited data on material performance at such high temperatures and pressure. Ni-based alloys have been of particular interest for use in the Gen IV SCWRs, due to their ability to maintain high strength and toughness at elevated temperatures. In this work, corrosion resistance of nickel-based Alloy 625, SS 310 and SS 304 was assessed at 625°C for 1000 h after being exposed to supercritical water (SCW), subcritical water (Sub-CW), and superheated steam; i.e., under pressures of 29, 8 and 0.1 MPa, respectively. The samples showed very small amount of weight gains after the exposure at 29 and 0.1 MPa, and a slight weight loss at 8 MPa due to pitting formation. The surface morphology and cross-section microstructure were analyzed using a Scanning Electron Microscope (SEM). The Energy Dispersive X-Ray Spectrometry (EDS) examination of the compositions of the surface oxide, indicated similar oxide formation on the top surface after exposures at different pressures, likely NiO or/and Ni(Cr,Al)₂O₄ type spinel. The implications of these results are discussed.

Chloride-induced stress corrosion crackingStress corrosion crack (CISCC) of austenitic stainless steel dry cask storage system (DCSS) canisters has been identified as an industry concern. Typical DCSS canisters are constructed from Types 304 or 316 stainless steel or their variants via conventional fusion welding processes. The presence of residual tensile stress and Cr-carbide precipitation within the weld heat affected zone (HAZ) places canisters near salt-bearing environments at an elevated risk for CISCC. The current study evaluates the suitability of friction stir processingFriction stir process (FSP) to repairRepair stress corrosion cracking (SCC) and remediate sensitized fusion weld HAZs. FSP was applied to furnace sensitized Type 304 specimens containing laboratory-generated SCC and evaluated using liquid penetrant inspection, phased array ultrasonic inspection, and optical microscopy. In addition, fusion welded Type 304L specimens were fabricated, subjected to FSP, and destructively analyzed via ASTM A262 and optical microscopy. Results demonstrate that FSP is a viable option for SCC repair and sensitizationSensitization remediation.

This study investigates the failure mechanisms of advanced oxidation resistant FeCrAl nuclear fuel cladding at high-strain rates, similar to conditions characteristic of design basis reactivity initiated accidentReactivity initiated accidents (RIAs). During a postulated RIA, the nuclear fuel cladding may be subjected to complex loading which can cause multiaxial strain states ranging from plane-strain to equibiaxial tension. To achieve those accident conditions, the samples were deformed by the expansion of high strength Inconel alloy tube under pre-specified pressure pulses, simulating strains rates occurring in a postulated RIA. The mechanical response of the advanced claddings, in the unirradiated state with ample ductility, was compared to that of hydrided zirconium-based nuclear fuel cladding. The hoop strain evolution pulses were collected in situ; the permanent diametral strains of both accident tolerant fuelAccident-tolerant fuel (ATF) claddings and the current nuclear fuel alloys were determined after rupture. Both zirconium-based alloys and FeCrAl alloysFeCrAl alloys exhibited ductile behavior. FeCrAl model alloys without microstructural control and strengthening mechanism were used in this demonstration study that showed reduced diametral strain (less than 0.15) compared to the diametral strain for the unirradiated zirconium-based alloy (approximately 0.2).

In this work we present a comparison of properties for U₃Si_2U3Si2, UNUN and UO₂ using first principles calculationFirst principle calculation. The local density approximation (LDA) and generalized gradient approximation (GGA/WC) predict that U₃Si₂ is non-magnetic while GGA/PBE predicts that ferromagnetic ordering (not observed experimentally) is more stable by just 0.02 eV per uranium atom. On the other hand, the ground states of Urania and UN are independent of the used functional, with a non-zero magnetic moment on uranium. U₃Si₂ is predicted to have lower binding energy (−14.4 eV) than UN (−20.4 eV) and UO₂ (−32.7 eV) and a lower melting point (1796 K vs. 2932 and 2987 K, respectively). The calculated minimal lattice thermal conductivity in W(m−1 K−1), indicates that phonon contribution to the thermal conductivity is smaller in both UN and U₃Si₂ (0.78 and 0.64 vs. 1.06). However calculations confirm that UN and U₃Si₂ are safer alternative fuelsNuclear alternative fuels due to their electronic thermal conductivity’s increasing with temperature as also observed experimentally.

Silicon CarbideSilicon carbide (SiC) and Beryllium OxideBeryllium oxide (BeO) are materials proposed to use in accident tolerant fuel. Therefore, we did a systematic study of the thermal conductivityThermal conductivity of SiC and BeO and its dependence on temperatures and structure by solving the Boltzmann transport equation using the shengBTE a solver for phonon thermal conductivity (k_L) with ab initio techniques. We also predict the structural, elastic, and thermodynamic properties of alpha-SiC, wurtzite (w)-SiC and w-BeO by first principles calculation using Quantum ESPRESSOQuantum ESPRESSO within quasi-harmonic approximation. k_L is also predicted using the Slack model. The thermo-mechanical properties of these materials show significant improvement over Urania with one order of magnitude higher thermal conductivity. Wurtzite structure shows the directional dependence of k_L. Hence, we provide the directional thermal conductivity of w-BeO, w-SiC and compare with the thermal conductivity of cubic SiC. The simulated results are compared with the available experimental data and showed excellent agreement.

Because of the manufacture process of high grade pipeline steel, the anisotropic behaviors appeared in different directions, including both properties and microstructureMicrostructure anisotropies. In this paper, mechanical propertiesMechanical properties anisotropies and microstructures for X100 high grade pipeline steelX100 high grade pipeline steel were investigated with a series of tests, including not only experiments but also simulation. Tensile tests with DIC (Digital Image Correlation) method was used to get the stress-strain relationship, especially in the process of fracture. SENT (Single Edge Notch Tensile) tests with different notch sizes were used to characterize the fracture resistance anisotropies. The microstructure was characterized by both fracture analysis and inclusion characteristicsInclusion characteristics to infer the relation between voids growth and crack propagationCrack propagation. Moreover, FE simulation of SENT was carried out by complete Gurson modelComplete Gurson model. Finally, the results of tests and simulations were compared to study the effects of stress constraintsStress constraints on crack resistance in different directions.

API 5L X70API 5L X70 M/MS line pipe steel grade has been very popular for the pipe manufacturing in sour/non-sour and offshore/onshore applications. This steel is available in various delivery conditions such as controlled rolling and TMCP with or without accelerated cooling. The selection of plate or coil depends on the type of pipe manufacturing and its final application. Co-relation of steel microstructure with tensile and toughness properties, before and after pipe manufacturing is required for the selection of suitable steel for a given application. For a given application and pipe manufacturing process, steel cleanliness, and allowance for Bauschinger effect, strain hardening, SCC and HIC resistance plays a prominent role. Present work is about microstructure and its co-relation with properties for X70 steel plates and coils supplied by 12 steel mills. Evaluation of alloy design with respect to microstructural features and its effect on tensile and toughness properties change from plate/coil to pipe is discussed.

In the present paper, an overview on the developments and applications of Ni-containing cryogenic steels is described with regard to the manufacturing processes. The relationship among Ni content, processing parameters and formation of reversed austenite has been worked out, which demonstrated that content and size of reversed austenite in Ni-containing steels can play important roles in improving their toughness. Based on extra-dephosphorization and desulphurization, new processing technologies have been developed. Controlled rolling in the aim of microstructure refinement and ultra-fast cooling (UFC) after hot rolling as on-line direct quenching has been successfully applied. Combining with inter-critical quenching and tempering after UFC-TMCP, the reversed austenite content was increased from 1.8 to 6.5%, leading to significant improvement of toughness. Several China’s steel works such as NISCO and Angang are capable of manufacturing high quality plates of Ni-containing steels, which are finding wide applications to building extra-large tanks for liquefied gases.

Stainless steel clad plate and pipe have a prevailing applications in nuclear power plants. The microstructure and mechanical properties of 304 austenite stainless steel clad plate by vacuum hot rolling were investigated in detail. Due to the severe diffusion of carbon element from carbon steel substrate to stainless steel clad, the decarburized layer and carburized layer were formed at the interfacial transition zone. The bending test reveals super-high interface strength and toughness, delaying the premature occurrence of interfacial delamination crack. The stainless steel clad pipe were successfully fabricated by elbowing and welding. There are no macroscopic and microscopic defects in the weld zone, fusion zone and heat affected zone. The heat affected zone of carbon steel layer contains widmanstatten, completely crystallized zone, partial crystallized zone and recrystallized zone. The weld zone of carbon steel contains widmanstatten structure and refined ferrite and pearlite. However, the heat affected zone is only comprised of coarse grains. With the increase of distance between weld zone and fusion zone, the small plane grain firstly changes into cellular crystal grain, and finally into columnar crystal in the stainless steel weld zone.

MicrostructureMicrostructure of pipeline steelsPipeline steel can be designed to meet the requirements of high performance pipeline steel. Grain or microstructure refinement is a key point for metallurgical design of high strengthHigh strength pipeline steel. A dual phase of ferrite and bainite microstructure design can be used for high deformability pipeline steel. Clean steel, no segregation, uniform microstructure and low hardness are basic requirements for pipeline steel used in sour environment. Microstructure and propertiesProperties of high performance pipeline steel developed in China recently are introduced in this paper.

As development of oil and gas expand into very high-pressure and high-temperature reservoirs, there is increasing interest in the development of nanomaterials to withstand these severe conditions. This paper reports on the comparison of the temperature behavior of nanomaterials used in the sensitivity analysis of hydrocarbon gases. The nanocomposite of tin dioxide (SnO₂) and zinc oxide (ZnO) were fabricated into sensor devices by the radio frequency sputtering method, and used for the characterization of the sensitivity behavior of methanol vapor. At different concentrations of the gases, the response of the sensor devices was analyzed at operating temperatures of 150–350 °C. Detailed analysis of the metal oxides thin film morphology and charge transportation of the sensor were collaborated with the response sensitivity in the target gases. Based on the behaviors of these nanomaterials, applications to oil and gas development could be adapted in residual petroleum reservoirs development.