Microstructural investigation and castability anticipation in modern Ti/Al/Nb-containing nickel-based superalloys

A quantitative relation between the γ/γ′ and γ/Laves intermetallics was investigated with the change of chemical composition, i.e., Ti, Al and Nb in the third generation of nickel-based superalloys. The results demonstrated that the maximum amount of intermetallic eutectics （i.e., 41.5%, mass fraction） has been formed in 9.8% （Ti＋Al）. It is predicted that high level of intermetallics formed in the 3GSA-HNM-1 （γ-9.8%（Ti＋Al）） deteriorates its castability. The type and morphology of eutectic intermetallics change and the amount considerably diminishes by decreasing Ti＋Al in 3GSA-HNM-2 （γ-7.6%（Ti＋Al）, 1.5% Nb）. Thus, it is predicted that the castability for the 3GSA-HNM-2 improves. The amount of Laves intermetallics shows an ascending behavior again, however, with less intensity by increasing the Nb content in the 3GSA-HNM-3 （γ-5.7%（Ti＋Al）, 2.9% Nb）. It can be concluded that for 3GSA-HNM-3 with composition of γ-5.7%（Ti＋Al） and 2.9% Nb, the optimized castability can be anticipated, because the minimum amount of eutectic intermetallics （i.e., 4.7%） is formed.

ADVANCED NICKEL-BASED AND NICKEL-IRON-BASED SUPERALLOYS FOR CIVIL ENGINEERING APPLICATIONS

The use of high-temperature materials is especially important in power station construction, heating systems engineering, furnace industry, chemical and petrochemical industry, waste incineration plants, coal gasification plants and for flying gas turbines in civil and military aircrafts and helicopters. Particularly in recent years, the development of new processes and the drive to improve the economics of existing processes have increased the requirements significantly so that it is necessary to change from well-proven materials to new alloys. Hitherto, heat resistant ferritic steels sufficed in conventional power station constructions for temperatures up to 550℃ newly developed ferritic/martensitic steels provide sufficient strength up to about 600 - 620℃. In new processes, e.g. fluidized-bed combustion of coal, process temperatures up to 900℃ occur. However, this is not the upper limit, since in combustion engines, e.g. gas turbines. Material temperatures up to 1100℃ are reached locally. Similar development trends can also be identified in the petrochemical industry and in the heat treatment and furnace engineering. The advance to ever higher material temperatures now not only has the consequence of having to use materials with enhanced high-strength properties, considerable attention now also has to be given to their chemical stability in corrosive media. Therefore not only examples of the use of high-temperature alloys for practical applications will be given but also be contributed to some general rules for material selection with regard to their high-temperature strength and corrosion resistance.

THE ROLE OF NIOBIUM IN NICKEL-BASED SUPERALLOYS AND CHARACTERIZATION OF PM ALLOY EP741NP

The role of niobium in nickel-based superalloys is reviewed. The importance of niobium as a strengthener is discussed. New developments in nickel-based superalloys are also briefly mentioned, including some results that show improved resistance to sulfidation by niobium. Research results from a current program on the role of niobium in the Russian powder metallurgy alloy EP741NP are presented. Future research plans on the role of niobium in superalloys are also discussed.

Review on synergistic damage effect of irradiation and corrosion on reactor structural alloys

The synergistic damage effect of irradiation and corrosion of reactor structural materials has been a prominent research focus.This paper provides a comprehensive review of the synergistic effects on the third-and fourth-generation fission nuclear energy structural materials used in pressurized water reactors and molten salt reactors.The competitive mechanisms of multiple influencing factors,such as the irradiation dose,corrosion type,and environmental temperature,are summarized in this paper.Conceptual approaches are proposed to alleviate the synergistic damage caused by irradiation and corrosion,thereby promoting in-depth research in the future and solving this key challenge for the structural materials used in reactors.

Nickel-base superalloys for USC power plants

The advanced ultra-supercritical power plants of the future will utilize steam pressures and temperatures that are too high for traditional ferritic steels,thus requiring austenitic materials.Older nickel-base superalloys such as 263 and 617 were initially evaluated under the European THERMIE project beginning in the 1990s.An entirely new age-hardened alloy 740 which possesses exceptional fireside corrosion resistance and creep strength was also developed for boiler tubing capable of serving at 700C.Subsequently,interest in the USA considered other product forms such as steam header piping and steam turbine forgings for service as high as 760C.A more stable and weldable alloy version now called 740H was developed to meet these more demanding conditions.This paper summarizes the current status of work on alloys 740 and 740H.

Electronic Properties of Passive Films Formed on G3 and G30 Nickel-based Alloys in Bicarbonate/Carbonate Buffer Solution

The electronic properties of passive films formed on G3 and G30 alloys in bicarbonate/carbonate buffer solution were comparatively studied by electrochemical impedance spectra（EIS） and Mott-Schottky analysis, the chemical composition of the passive film formed on G3 alloy was detected by X-ray photoelectron spectroscopy （XPS）. The results show that passive film on G3 alloy had better protection than that on G30 alloy. The transfer resistance, film resistance and diffusion resistance of the passive films on both alloys increased with increasing formation potential, prolonging formation time, increasing pH value, decreasing formation temperature, and decreasing chloride and sulphide ions concentration. Mott-Schottky plot reveals that the passive films on the two alloys show a p-n semi-conductive character. XPS analysis indicates that the passive film on G3 alloy was composed of an inner Cr oxide and an outer Fe, Mo/Ni oxides.

Corrosion performance and applicability evaluation of nickel-based alloys for oil and gas production tubing applications

The sulfide stress corrosion cracking（ SSC） performance of G3 and 028 nickel-based alloys w as studied using slow strain rate test（ SSRT） and the four-point bend（ FPB） test under simulated dow nhole conditions. The effect of high temperature,high H2 S / CO2 partial pressure,and the presence of sulfur on SSC susceptibility w as investigated. The G3 alloy w as found to have a higher SSC resistance than the 028 alloy. Presence of sulfur and temperature bear a strong influence on the SSC performance of the metals,particularly on the 028 alloy. The applicability of 028 and G3 alloys may be expanded and both could safely be used beyond the limits set by the ISO15156-3 standard.

Research on CMT welding of nickel-based alloy with stainless steel

Cold Metal Transfer （CMT） welding technique is a new welding technique introduced by Fronins company. CMT welding of nickel-based alloy with stainless steel was carried out using CuSi3 filler wire in this paper. Effects of welding parameters, including welding current, welding speed, etc, on weld surface appearance were tested. Microstructure and mechanical properties of CMT weld were studied. The results shaw that the thickness of interface reaction layer of the nickel- based alloy is 14. 3 μm, which is only 4. 33% of base material. The weld is made up of two phases, α-copper and iron-based solid solution. Rupture occurs initially at the welded seam near the edge of stainless steel in shear test. The maximum shear strength of the CuSi3 welded joint is 184. 9 MPa.

Simulation and experiments of ultrasonic propagation in nickel-based alloy weldments

In order to obtain good understanding of complicated beam propagation behaviors in nickel-based alloy weldments , ray tracing simulation is established to predict the ultrasonic beam path in a special welded structure of dissimilar steels. Also experimental examinations are carried out to measure the ultrasonic beam paths in the weldment. Then comparisons of the modeling predictions with experimental results are presented to reveal the complicated beam propagation behaviors.

NICKEL-BASE ALLOY SHEET ALLOYS USED IN AEROSPACE APPLICATIONS

Many gas turbine components are made from nickel alloy sheet. Most are used for directing or containing gases at high temperatures and pressures where metal temperatures can be as high as 1090℃ (2000°F). These applications included combustor systems, casings and liners, transition and exhaust ducting, afterburners, and thrust reversere. Light weight components and sub-assemblies call for alloy sheet with high levels of stength and oxidation resistance. Complex component design calls for excellent ductility and ease of fabrication.The wide range of nickel alloy sheet alloys presently used in aircraft and land-based gas turbines is briefly described and typical properties presented. New sheet alloy developments, involving INCONEL￣* alloys 625LCF, 718SPF and MA754, are presented including the process routes involved and material properties.

The Heat Treatment Behavior of Super-High Strength Aluminum Alloys by Spray Forming

In order to understand the stress corrosion behavior of super-high strength aluminum alloys by spray forming, different aluminum alloys by different heat treatment was made. The results showed that the alloy with peak aging has the most sensitive stress corrosion cracking, the crack can even be seen using eyes;the alloys with two step aging were better than one step aging alloys, the alloys has not been found stress corrosion cracking.

Evolution of helium bubbles in nickel-based alloy by post-implantation annealing

Nickel-based alloys have been considered as candidate structural materials used in generation IV nuclear reactors serving at high temperatures.In the present study,alloy 617 was irradiated with 180-keV helium ions to a fluence of 3.6×10^(17) ions/cm^(2) at room temperature.Throughout the cross-section transmission electron microscopy(TEM)image,numerous over-pressurized helium bubbles in spherical shape are observed with the actual concentration profile a little deeper than the SRIM predicted result.Post-implantation annealing was conducted at 700℃for 2 h to investigate the bubble evolution.The long-range migration of helium bubbles occurred during the annealing process,which makes the bubbles of the peak region transform into a faceted shape as well.Then the coarsening mechanism of helium bubbles at different depths is discussed and related to the migration and coalescence(MC)mechanism.With the diffusion of nickel atoms slowed down by the alloy elements,the migration and coalescence of bubbles are suppressed in alloy 617,leading to a better helium irradiation resistance.

Property uniformity of thick nickel-based alloy plate for nuclear power steam-generator divider plate

This paper introduces a thick 690 nickel-based alloy plate produced by the former Baosteel Special Steel Co.,Ltd.used as the steam-generator divider plate in the pressurized water reactor nuclear power plant.According to the product characteristics and design requirements of the thick nickel-based alloy plate,multidimensional sampling and testing were conducted to investigate its microstructure and mechanical properties.The results show that all the property indexes of the thick hot-rolled nickel-based alloy plate meet the design requirements,and there is good uniformity in the microstructure and mechanical properties in different dimensions.These findings indicate that China has mastered the core manufacturing technology of thick nickel-based alloy plates for their use as divider plates in nuclear power steam generators.

海洋平台海水系统新材料适用性研究

海洋平台利用周围取之不尽的海水作为平台的工艺处理介质已成常规做法。因为海水利用的普通性、经济性以及重要性,对于海水系统选材通常涉及到的使用寿命、制造成本、耐腐蚀性能等多个方面研究值得关注。对常用的几种海水管道材料进行了系统的比较和评价,并介绍了一些新型材料应用前景。在综合考虑各种材料的优劣后,提出了一种最适合海洋平台海水系统的选材方案,并阐述了其理由和依据。旨在为海洋平台海水系统设计和施工提供借鉴。

碳中和目标下新一代超高参数煤电机组技术体系

该文围绕“双碳”目标,分析煤电对支撑我国新型电力系统的重要作用以及燃煤发电技术的主要发展方向,提出下一代超超临界燃煤发电技术体系,并简要介绍相关研发实践。该技术体系基于国产化的HT700系列高温合金材料,耦合高参数煤电、煤电灵活性、烟气污染物低温氧化吸附(cold oxidation adsorption process,COAP与COAP+)脱除近零排放技术、碳补集、利用与封存技术(carboncapture,utilization and storage,CCUS)、数字化智能化及燃煤耦合多源固废发电等前沿技术,建议开发新一代超高参数燃煤发电机组,实现机组煤耗与能耗水平、运行稳定性、灵活性的有机统一,支撑我国“双碳”目标的实现。

精细金属掩模板用近零夹杂Invar合金制备技术

Invar合金是制备精细金属掩模板(Fine Metal Mask,简称FMM)的重要基材,其纯净度直接影响FMM的质量以及有机发光二极管(Organic Light EmittingDiode,简称OLED)技术的发展水平。首先概述了FMM的主要制备技术,介绍了对FMM基材Invar合金的质量要求,并对国产Invar合金箔和国外进口Invar合金箔内的夹杂物进行了表征分析。结果表明,国产Invar合金箔的纯净度与进口Invar合金箔相比,仍存在很大的差距,主要体现在夹杂物的尺寸和数量等方面。为实现OLED配套产业全国产化,攻克Invar合金的近零夹杂难题,开发新型制备技术是关键突破点。最后详细论述了超重力技术在Invar合金除杂方面的研究成果和电铸Invar合金箔应用的可行性,并指出超重力技术和电铸技术有望解决近零夹杂金属材料的制备难题。

激光选区熔化技术制备NiTi合金的研究进展与应用

NiTi合金作为一种典型的形状记忆合金,除了具有独特的形状记忆效应,还拥有优异的超弹性、生物相容性和力学性能,广泛应用于医学、机械、微电子等领域。然而,由于该合金延展性过高、加工硬化、低热导等问题,传统的切削方法加工工艺复杂、成本高,限制了其工程化应用。增材制造技术(Additive manufacturing, AM)又称3D打印技术,以其独特的一体化成形的技术优势,有效地改善了传统加工方法存在的问题。对此,国内外学者对激光选区熔化(SLM) 3D打印镍钛合金成形工艺进行了大量研究,并取得了丰硕成果。综述了近年来选区激光熔化镍钛的研究进展,简述了选区激光熔化和热处理工艺与镍钛合金的相变温度、组织结构、力学性能等映射关系,着重分析了SLM工艺参数对镍钛合金超弹性的影响规律,揭示了其影响机制,介绍了激光选区熔化镍钛合金的在医学领域的应用,并对未来NiTi合金的增材制造技术的发展提出了展望。

DD5缓进磨削表面粗糙度和硬化率对疲劳性能影响研究

为研究DD5镍基单晶高温合金缓进磨削表面粗糙度和硬化率对疲劳性能的影响规律及机理,设计实验并进行了试件磨削与疲劳性能测试。结果表明:表面粗糙度的增大引起应力集中加剧,导致疲劳性能降低,不同磨削工艺下表面粗糙度由0.347μm增大到0.687μm,其疲劳寿命由5.51×10^(5)降至3.38×10^(5),下降率约38.66%;表面粗糙度小于0.4μm时表面硬化可提高试件疲劳寿命,表面粗糙度超过0.4μm时表面硬化对疲劳性能的影响不显著;形貌测试结果表明,随着表面粗糙度的提高,磨削表面耕犁产生的沟壑数量和深度均增大,疲劳载荷作用下磨削表面裂纹源数量增加、应力集中加剧,从而导致疲劳寿命降低。较小的表面粗糙度与较大的表面硬化率均可提高DD5缓进磨削疲劳性能。

纳米晶合金粉芯的超重力渗流制备及磁性能

为了探索粉芯的新制备工艺,以Fe_(73.5)Cu_(1)Nb_(3)Si1_(3.5)B_(9)纳米晶合金铁芯为原料,使用机械破碎法制粉,并采用超重力渗流工艺制备了7种不同粒度配比的纳米晶合金粉芯,借助SEM、XRD、VSM分别对纳米晶粉末的形貌、结构和磁性能进行了表征,研究了粉末粒度配比对纳米晶合金粉芯的形貌、密度、有效磁导率、损耗及品质因数的影响。结果表明,机械破碎法制得的粉末虽带尖角,但矫顽力低,利用超重力渗流工艺制备的粉芯其粉末表面基本被树脂完全包覆。同时,通过适当的粉末粒度匹配,发现性能最佳粉芯的粉末粒度配比为:100~200目占60%,200~400目占20%,400~1000目占20%。该种粉芯的密度为4.46 g∕cm^(3),在100~3000 kHz频率范围内有效磁导率比较稳定,且在3000 kHz时为28.2。当设定磁感应强度为20 mT,频率为500 kHz时,其损耗为99.1 W/kg。另外,根据实验结果可知,该工艺能够制备出频率在MHz以上具有较低损耗的粉芯。

微量元素对K418B合金显微组织和力学性能的影响

研究了微量元素Mg对K418B合金铸态组织以及力学性能的影响。采用热力学计算软件JMatPro对K418B合金中相的稳定性及体积百分比进行计算。借助附带的能谱仪(EDS)的扫描电镜(SEM)对两种合金的显微组织及其成分进行分析。使用Image-Pro Plus软件对碳化物、γ′相和共晶相的尺寸以及体积分数进行统计分析。拉伸性能测试分别按照HB 5143和HB 5195的规定在23℃(室温)和750℃(中温)下进行。760℃/530 MPa和982℃/152 MPa持久测试按照HB5150进行。结果表明加Mg后对K418B合金的力学性能有所提升。