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Processing of a low-cost γ-γ' NiPtAl coating with improved oxidation resistance

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Rare Metals 2024年第6期43卷 2832-2841页

作者： Yan Jiang Liang-Liang Wei Jian He Hong-Bo Guo school of materials Science and engineering Beihang University Key Laboratory of high-temperature Structural materials and Protective Coatings Ministry of Industry and Information TechnologyBeihang University

A novel γ-γ'（Ni solid solution—Ni3Al） NiPtAl coating was produced on advanced single-crystal（SC）superalloy N5 by electroplating of a thin Pt coating with～3 μm in thickness followed by heat treatment at 1000 ℃ in vacuum.For comparison,a traditional γ-γ'NiPtAl coating was also produced by electroplating of a thick Pt coating with ～ 6 μm in thickness followed by heat treatment at 1100 ℃ in vacuum.The novel coating has a mass gain of～ 0.5 mg·cm-2after 100 h 1-h cyclic oxidation at 1150℃,showing better oxidation resistance than the traditional coating.An oxide scale mostly consisting of α-Al2O3grew on the novel coating because the element Cr from the SC alloy substrate contributes to the formation of α-Al2O3.Pt content in the novel coating has significant effect on the oxidation resistance.The optimized Pt content in the coating is about 16 at%,which is helpful to reduce the diffusion of harmful elements from the substrate into the coating but also to reduce the cost of the coating.

关键词： γ–γ′ NiPtAl coating Platinum Oxidation Al 2 O 3 Superalloy

Precipitation kinetics and strengthening of M23C6 in novel G115 martensitic steel:Utilizing secondary normalizing

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Progress in Natural Science:materials International 2024年第2期34卷 396-407页

作者： Chengxian Zhang Zhi Yuan Qiuzhi Gao Qingshuang Ma Hailian Zhang Jing Bai Huijie Zhang Liming Yu Huijun Li school of materials Science and engineering Northeastern University school of resources and materials Northeastern University at Qinhuangdao school of materials Science & engineering Tianjin University school of Mechanical Materials and Mechatronic Engineering University of Wollongong

G115 martensitic steel is anticipated to be one of the preferred candidate materials in ultra-super critical(USC)power plants with steam temperatures above 650℃.Microstructure evolutions and mechanical properties of G115 martensitic steel after applying various heat treatment processes were investigated.The results demonstrate that the main precipitate in G115 martensitic steel after applying various heat treatment processes is M23C6 phase with Cr enrichment.The time required for M23C6 phase precipitation decreases with increasing secondary normalizing temperature and the extension in holding time according to its precipitation-temperature-time(PTT)curves.Volume fraction of M23C6 phase increases with increasing secondary normalizing temperature and holding time,which strengthens the inhibitory effect of precipitates on dislocations recovery and laths growth.Therefore,G115 martensitic steel can obtain the best mechanical properties after applying the highest secondary normalizing temperature and the longest holding time.In the current work,the excellent strength of G115 martensitic steel mainly derives from precipitates strengthening and laths strengthening.

关键词： G115 martensitic steel M23C6 phase Precipitation kinetics Secondary normalizing Strengthening mechanisms

Hydrolysis mechanism of YbB_(2)C_(2)and the microstructure of the carbon derived from the hydrolysis reaction

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Journal of materials Science & Technology 2024年第4期171卷 209-221页

作者： Zhihui Li Hao Zhang Jixin Chen Jiemin Wang Xiaohui Wang Jinxing Yang Chao Zhang Zerong Zhang Hongyang Liu Fei Huang Meishuan Li Fei Li Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China school of materials Science and engineering University of Science and Technology of ChinaShenyang 110016China Shanghai Key Laboratory for high temperature materials and Precision Forming School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Carbide-derived carbon(CDC)materials have gained great attention due to the excellent properties for various potential applications.Here,graphite crystal is formed during a room-temperature hydrolysis pro-cess of layered compound YbB_(2)C_(2).The formation mechanism can be demonstrated by a YbB_(2)C_(2)molecular cell:Yb^(3+)acts as a cathode where H_(2)O molecule is reduced to H atom and OH^(−)ion,while(B_(2)C_(2))^(3−)acts as an anode where OH−ion is oxidized to O atom.Then,YbB_(2)C_(2)molecular cell begins to disintegrate,i.e.,Yb^(3+)ion,B and C atoms dissociate from the molecular cell.The as-produced C atoms combine to form graphite crystal.The initial graphite crystal is a cabbage-like microsphere,and then it gradually disintegrates and transforms into layered graphite.In addition,YbB_(6),Yb_(3)(OH)_(3)n(BO_(3))_((3-n))sol,hydrogen,hydrocarbons,and carbon oxides form simultaneously.Our method provides a general and inexpensive route to obtain carbide-derived graphite crystal.

关键词： Carbide-derived carbon YbB_(2)C_(2) Hydrolysis Molecular cell First-principles calculations

Corrosion of Duplex Stainless Steel Manufactured by Laser Powder Bed Fusion: A Critical Review

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Acta Metallurgica Sinica(English Letters) 2024年第4期37卷 587-606页

作者： Yiqi Zhou Decheng Kong Ruixue Li Xing He Chaofang Dong Beijing Advanced Innovation Center for materials Genome engineering Institute for Advanced Materials and TechnologyUniversity of Science and Technology BeijingBeijing100083China Shanghai Key Laboratory of Advanced high-temperature materials and Precision Forming School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai200240China

Laser powder bed fusion (LPBF) is a commonly used additive manufacturing (AM) method for efficiently producing intricate geometric components. This investigation examines factors such as pores, cellular structure, grain size, and inclusions from the manufacturing process that contribute to the corrosion resistance of LPBF DSS. Furthermore, the as-built LPBF duplex stainless steel (DSS) is primarily ferrite due to the rapid cooling process. Therefore, the transformation of ferrite to austenite after various heat treatments in LPBF DSS and its corresponding corrosion resistance are presented. Additionally, a new mixed powder method is proposed to increase the austenite content in the as-built LPBF DSS. This review also focuses on the passivation capability and pitting corrosion performance in LPBF and conventional DSS. This article summarizes the variations in microstructure between as-built and heat-treated LPBF DSS, with their impacts on corrosion resistance, offering insights for manufacturing highly corrosion-resistant LPBF DSS.

关键词： Laser powder bed fusion Duplex stainless steel Microstructure Heat treatment Passivation Pitting corrosion

Characteristics and stability of oxide+carbonitride in H13 steel at 1250℃

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Journal of Iron and Steel Research(International) 2024年第1期31卷 134-142页

作者： Xiao-lin Sun Han-jie Guo Jing Guo Fei Wang Dong Xu Gao-yang Song Shuai Wang school of materials Science and engineering Hebei University of EngineeringHandan056038HebeiChina school of Metallurgical and Ecological engineering University of Science and Technology BeijingBeijing100083China high temperature materials Research Institute Central Iron and Steel Research Institute Co.Ltd.Beijing100081China Technology Innovation Center for high Quality Cold Heading Steel of Hebei Province Hebei University of EngineeringHandan056038HebeiChina

The morphology,size,quantity,and composition of complex oxide+carbonitride in H13 steel held at 1250℃for 5,10,and 15 h were determined.The results show that the ratio and number of complex carbonitrides with cores in H13 steel are gradually increased when holding at 1250℃compared with those in the original H13 steel,and the core size increases.There are one or more oxide cores in(Ti_(x),V_(1-x))(Cy,N_(1-y)),including xCaO·zAl_(2)O_(3),xCaO·yMgO·zAl_(2)O_(3),and CaO after holding at 1250℃,in addition to MgO·Al_(2)O_(3)and Al_(2)O_(3)in the original steel.The equilibrium temperature for(Ti_(x),V_(1-x))(Cy,N_(1-y))precipitation at the solidification front and decomposition in the solid state was theoretically analyzed,which was affected by the x value and the product of Ti and N contents in H13 steel.Meanwhile,the composition of(Ti_(x),V_(1-x))(Cy,N_(1-y))is influenced by the oxide cores.It is convinced that(Ti_(x),V_(1-x))(Cy,N_(1-y))with oxide cores has a higher stability,especially for oxides with a high Al_(2)O_(3)content.Heat treatment at high temperature facilitates a more reasonable analysis of oxide+carbonitride,and the generation mechanism of oxide+carbonitride was discussed.

关键词： Complex carbonitride Decomposition Oxide core Characteristic Stability

Oxidation behavior of 4774DD1 Ni-based single-crystal superalloy at 980℃ in air

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China Foundry 2024年第2期21卷 116-124页

作者： Yu Fang Ya-zhou Li Qiang Yang Qun-gong He Xiu-fang Gong Qian Duan Hai-yang Song Fu Wang Qiong-yuan Zhang Hong Zeng State Key Laboratory of Long-Life high temperature materials Dongfang Turbine Co.Ltd.Deyang 618000SichuanChina State Key Laboratory for Manufacturing System engineering School of Mechanical EngineeringXi’an Jiaotong UniversityXi’an 710049China

The oxidation behavior of a novel Ni-based single-crystal 4774DD1 superalloy for industrial gas turbine applications was investigated by the isothermal oxidation at 980℃ and discontinuous oxidation weight gain methods.The phase constitution and morphology of surface oxides and the characteristics of the crosssection oxide film were analyzed by XRD,SEM and EDS.Results show that the oxidation kinetics of the 4774DD1 superalloy follows the cubic law,indicating its weak oxidation resistance at this temperature.As the oxidation time increases,the composition of the oxide film evolves as following:One layer consisting of a bottom Al_(2)O_(3)sublayer and an upper(Al_(2)O_(3)+NiO)mixture sublayer after oxidized for 25 h.Then,two layers composed of an outermost small NiO discontinuous grain layer and an internal layer for 75 h.This internal layer is consisted of the bottom Al_(2)O_(3)sublayer,an intermediate narrow CrTaO_(4)sublayer,and an upper(Al_(2)O_(3)+NiO)mixture sublayer.Also two layers comprising an outermost relative continuous NiO layer with large grain size and an internal layer as the oxidation time increases to 125 h.This internal layer is composed of the upper(Al_(2)O_(3)+NiO)mixture sublayer,an intermediate continuous(CrTaO_(4)+NiWO_(4))mixture sublayer,and a bottom Al_(2)O_(3)sublayer.Finally,three layers consisting of an outermost(NiAl2O_(4)+NiCr2O_(4))mixture layer,an intermediate(CrTaO_(4)+NiWO_(4))mixture layer,and a bottom Al_(2)O_(3)layer for 200 h.

关键词： nickel-base single crystal superalloy oxidation kinetics oxide film microstructure mechanism

On-surface synthesis and characterization of polyynic carbon chains

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National Science Review 2024年第3期11卷 192-199页

作者： Wenze Gao Wei Zheng Luye Sun Faming Kang Zheng Zhou Wei Xu Interdisciplinary materials Research Center School of Materials Science and Engineering Tongji University

Carbyne, an elusive sp-hybridized linear carbon allotrope, has fascinated chemists and physicists for decades. Due to its high chemical reactivity and extreme instability, carbyne was much less explored in contrast to the sp2-hybridized carbon allotropes such as graphene. Herein, we report the on-surface synthesis of polyynic carbon chains by demetallization of organometallic polyynes on the Au（111） surface;the longest one observed consists of ～60 alkyne units（120 carbon atoms）. The polyynic structure of carbon chains with alternating triple and single bonds was unambiguously revealed by bond-resolved atomic force microscopy. Moreover, an atomically precise polyyne, C14, was successfully produced via tip-induced dehalogenation and ring-opening of the decachloroanthracene molecule(C14Cl10) on a bilayer NaCl/Au（111） surface at 4.7 K, and a band gap of 5.8 eV was measured by scanning tunnelling spectroscopy,in a good agreement with the theoretical HOMO–LUMO gap（5.48 eV）.

关键词： polyyne scanning probe microscopy carbon allotrope on-surface synthesis organometallic polyyne

Recent process developments in beneficiation and metallurgy of rare earths:A review

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Journal of Rare Earths 2024年第4期42卷 629-642页

作者： Shaokai Cheng Wenbo Li Yuexin Han Yongsheng Sun Peng Gao Xiaolong Zhang school of resources and Civil engineering Northeastern UniversityShenyang110819China National-local Joint engineering Research Center of high-efficient Exploitation Technology for Refractory Iron Ore resources Shenyang110819China

Rare earth elements(REEs)are irreplaceable materials supporting low-carbon technology and equip-ment,and their commercial demand and strategic position are becoming increasingly prominent.With the continuous depletion of rare earth(RE)resources,developing high-efficiency beneficiation and eco-friendly metallurgical processes has attracted widespread attention.This paper reviews the major minerals exploited for RE production and their deposits,as well as the beneficiation and metallurgical processes of RE minerals.Bastnaesite,monazite,mixed RE ores,and ion-adsorption clays are the main raw materials in the world to date.RE-bearing ores(except ion-adsorption minerals)are generally beneficiated by flotation,gravity and magnetic separation techniques.The mainstream metallurgical processes for bastnaesite,monazite and mixed RE concentrates are oxidation roasting-HCl leaching,caustic soda decomposition and high-temperature concentrated sulfuric acid roasting,respectively.Ion-adsorption clays are directly processed by in situ leaching-precipitation/solvent extraction.To achieve the sustainable development of RE resources,it is essential to further explore innovative techniques to achievecomprehensive utilization and cleaner production.

关键词： Rare earths Beneficiation processes Metallurgical processes Cleaner production

Recent advances in the biosynthesis of coumarin and its derivatives

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Green Chemical engineering 2024年第2期5卷 150-154页

作者： Yusong Zou Yuxi Teng Joy Li Yajun Yan school of Chemical Materials and Biomedical EngineeringCollege of EngineeringThe University of GeorgiaAthensGA30602USA North Oconee high school BogartGA30622USA

Coumarin and its derivatives,presenting in many organisms(plants,fungi,and bacteria),are critical metabolites composed of fused benzene andα-pyrone rings.With unique biological and chemical properties,coumarin derivatives possess great technological potential in the agrochemicals,pharmaceuticals,food,and cosmetic industries.The increasing demand for coumarin derivatives accelerates the research in biological and chemical synthesis to provide stable and scalable sources of coumarins.However,the complex structures and unknown pathways have limited the progress in the biosynthesis of coumarin derivatives.Here,we summarize recent developments and provide a detailed analysis of coumarin derivative biosynthetic pathways in different organisms.

关键词： Coumarin derivatives Biosynthetic pathways Biotransformation Metabolic engineering