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Effect of Zr on undissolved phases and carbide precipitation in Ti microalloyed low-carbon steel

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Journal of Iron and Steel Research(International) 2019年第7期26卷 720-732页

作者： Peng-cheng Liu Jian-chun Cao Shu-biao Yin Yin-hui Yang Peng Gao Faculty of Materials Science and Engineering Kunming University of Science and Technology Kunming 650093 Yunnan China Faculty of Metallurgical and Energy Engineering Kunming University of Science and Technology Kunming 650093 Yunnan China

The undissolved phases and carbide precipitation in Ti and Ti-Zr microalloyed low-carbon steels were investigated by scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectrometry. At 1225℃, the replacement of Ti by Zr formed Zr2CS and (Zr, Ti)N (the Ti/Zr atomic ratio is 0.11) and reduced the consumption of Ti. At 925℃, it was identified that TiC phases were precipitated at first and Zr was incorporated into the TiC lattice in the subsequent precipitation process, which promoted the precipitation of titanium carbide. The calculation of the interaction coefficient between Ti, C, N and Zr showed that Zr reduced the activity of Ti and C and increased the activity of N in the iron matrix. Therefore, with the addition of Zr, the solubility of Ti was increased, and the consumption of Ti was reduced at high temperature in Ti microalloyed low-carbon steel. The thermodynamic calculation of carbide precipitation transformation showed that the replacement of Ti by Zr increased the nucleation driving force and the nucleation rate of titanium carbide, while the critical core size and the critical nuclear energy were reduced. As the holding time was extended, the Zr/ Ti atomic ratio increased and the size of the precipitates also increased. When the Zr/Ti atomic ratio reached a certain level, the size of the precipitates did not increase with further increase in atomic ratio. When the Zr/Ti atomic ratio in (Ti, Zr)C was 0.05-0.17,(Ti, Zr)C was the most stable carbide and the easiest to nucleate at 925℃. There was more of the (Ti, Zr)C phase than TiC at 925 ℃ after 50 and 100 s, and the time to complete the coarsening behavior of (Ti, Zr)C was shorter than that of TiC.

关键词： Ti-Zr microalloyed steel Undissolved phase carbide precipitation Zirconium Thermodynamics

Diffusion mechanism in molten salt baths during the production of carbide coatings via thermal reactive diffusion

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International Journal of Minerals,Metallurgy and Materials 2017年第12期24卷 1448-1458页

作者： Aliakbar Ghadi Hassan Saghafian Mansour Soltanieh Zhi-gang Yang Center of Excellence for High Strength Alloys Technology School of Metallurgy and Materials EngineeringIran University of Science and Technology Key Laboratory of Advanced Materials of Ministry of Education School of Materials Science and EngineeringTsinghua University

The diffusion mechanism of carbide-forming elements from a molten salt bath to a substrate surface was studied in this research, with particular focus on the processes occurring in the molten bath at the time of coating. Metal, oxide, and metal-oxide baths were investigated, and the coating process was performed on H13 steel substrates. Scanning electron microscopy and electron-probe microanalysis were used to study the coated samples and the quenched salt bath. The thickness of the carbide coating layer was 6.5 ± 0.5, 5.2 ± 0.5, or 5.7 ± 0.5 μm depending on whether it was deposited in a metal, oxide, or metal-oxide bath, respectively. The phase distribution of vanadium-rich regions was 63%, 57%, and 74% of the total coating deposited in metal, oxide, and metal-oxide baths, respectively. The results obtained using the metal bath indicated that undissolved suspended metal particles deposited onto the substrate surface. Then, carbon subsequently diffused to the substrate surface and reacted with the metal particles to form the carbides. In the oxide bath, oxide powders dissolved in the bath with or without binding to the oxidative structure(Na_2O) of borax; they were then reduced by aluminum and converted into metal particles. We concluded that, in the metal and oxide baths, the deposition of metal particles onto the sample surface is an important step in the formation of the coating.

关键词： thermal reactive diffusion diffusion mechanism carbide coating films metal particles borax bath

Effects of cobalt carbide on Fischer–Tropsch synthesis with MnO supported Co-based catalysts

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Journal of Energy Chemistry 2020年第3期29卷 227-232页

作者： Fanfei Sun Ruoou Yang Zhaoming Xia Yuqi Yang Ziang Zhao Songqi Gu Dongshuang Wu Yunjie Ding Zheng Jiang Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201204China Shanghai Synchrotron Radiation Facility Zhangjiang LaboratoryShanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China University of Chinese Academy of Sciences Beijing 100100China Center for Applied Chemical Research Frontier Institute of Science and TechnologyXi’an Jiaotong UniversityXi’an 710049ShaanxiChina Dalian National Laboratory for Clean Energy Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina Graduate school of science Kyoto UniversityKitashirakawaOiwake-choSakyo-kuKyoto-shiKyoto-fu606-8502Japan

Cobalt carbide(Co2C)was considered as potential catalysts available for large-scale industrialization of transforming syngas(H2 and CO)to clean fuels.Herein,we successfully synthesized Co-based catalysts with MnO supported,to comprehend the effects of Co2C for Fischer–Tropsch synthesis(FTS)under ambient conditions.The huge variety of product selectivity which was contained by different active sites(Co and Co2C)has been found.Furthermore,density functional theory(DFT)shows that Co2C is efficacious of CO adsorption,whereas is weaker for H adsorption than Co.Combining the advantages of Co and Co2C,the catalyst herein can not only obtain more C5+products but also suppress methane selectivity.It can be a commendable guide for the design of industrial application products in FTS.

关键词： Cobalt carbide Fischer–Tropsch synthesis X-ray absorption fine spectroscopy nanomaterials Density functional theory

Facile synthesis of molybdenum carbide nanoparticles in situ decorated on nitrogen-doped porous carbons for hydrogen evolution reaction

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Journal of Energy Chemistry 2019年第5期28卷 78-84页

作者： Jin-Tao Ren Yue-Jun Song Zhong-Yong Yuan National Institute for Advanced Materials School of Materials Science and EngineeringNankai UniversityTianjin 300350China Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) Collaborative Innovation Center of Chemical Science and Engineering (Tianjin)Nankai UniversityTianjin 300071China

Molybdenum-based electrocatalysts are promising candidates of platinum (Pt)-based materials in electrocatalyzing hydrogen evolution reaction (HER), due to their cost-efficient and resembled electronic properties. Reported herein is the preparation of molybdenum carbide nanoparticles uniformly decorated on nitrogen-modified carbons (Mo2C/NC) through the carbonization of Mo-based polymers under hydrogen atmosphere by using poly(p-phenylenediamine) and ammonium heptamolybdate polymer analogue as precursors. And the molybdenum nitride nanoparticles loaded on porous N-doped carbons (Mo2N/NC) are also fabricated by calcination the polymer precursors in nitrogen gas. The Mo2C/NC shows more excellent electrocatalytic activity than Mo2N/NC in 0.5 M H2SO4, together with robust long-term durability. The well-crystalline nanoparticles and the increased electron conductivity are the main characters responded for the high catalytic efficiency of the fabricated electrocatalysts. This easily fabrication procedure may provide a facile route to prepare non-noble metal carbide/nitride catalysts featuring wellengineered structural and textural peculiarities for realistic energy conversion system.

关键词： Molybdenum carbide Molybdenum nitride Nitrogen-doped carbon Hydrogen evolution reaction Electrocatalysis

THERMAL SHOCK FATIGUE BEHAVIORS OF CEMENTED carbide YG20

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中国有色金属学会会刊：英文版 1997年第2期7卷 150-155页

作者： Liu, Ning Xu, Genying Xu, Yudong Li, Jian Anhui Inst of Technology Hefei China

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ＴＨＥＲＭＡＬＳＨＯＣＫＦＡＴＩＧＵＥＢＥＨＡＶＩＯＲＳＯＦＣＥＭＥＮＴＥＤＣＡＲＢＩＤＥＹＧ２０①ＬｉｕＮｉｎｇ，ＸｕＧｅｎｙｉｎｇ，ＸｕＹｕｄｏｎｇＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｒｉｎｇ，ＡｎｈｕｉＩｎ...

关键词： cemented carbide YG20 thermal shock fatigue crack formation microvoid

carbide PRECIPITATION AND BAINITE TRANSFORMATION IN Fe-C-Si ALLOY

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Acta Metallurgica Sinica(English Letters) 1996年第5期9卷 373-378页

作者： R.L. Zuo L. Fang and P. D. Ding(Department of Metallurgy and Materials Engineering, Chongqing University, Chongqing 630044, China)

The upper bainite formed isothermally at 480℃ C in Fe-0. 38C-1. 73Si alloy was studied by using transmission electron microscopy (TEM). It was found by electron diffraction and crystallographic analysis that bainitic carbide precipitation originated from bainitic ferrite (BF), in which the initial supersaturation did not come up to the average carbon content of the alloy. It is suggested that bainite transformation in steel should be a coupled process of transformation dislocation movement controlled by carbon diffusion in austenite.

关键词： bainite carbide shear dislocation

Finite element simulation of the micromachining of nanosized-silicon-carbide-particle reinforced composite materials based on the cohesive zone model

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Nanotechnology and Precision Engineering 2018年第4期1卷 242-247页

作者： Hongmin Pen Jianhua Guo Zizhen Cao Xianchong Wang Zhiguo Wang Tianjin Institute of Aerospace Mechanical and Electrical Equipment Tianjin 300458China Tianjin Long March Technical Equipment Co.Ltd. Tianjin 300462China Guilin University of Aerospace Technology Guilin 541000China

A finite element method based on the cohesive zone model was used to study the micromachining process of nanosized silicon-carbide-particle(SiCp) reinforced aluminum matrix composites. As a hierarchical multiscale simulation method, the parameters for the cohesive zone model were obtained from the stress-displacement curves of the molecular dynamics simulation. The model considers the random properties of the siliconcarbide-particle distribution and the interface of bonding between the silicon carbide particles and the matrix.The machining mechanics was analyzed according to the chip morphology, stress distribution, cutting temperature, and cutting force. The simulation results revealed that the random distribution of nanosized SiCp causes non-uniform interaction between the tool and the reinforcement particles. This deformation mechanics leads to inhomogeneous stress distribution and irregular cutting force variation.

关键词： Multiscale Cohesive zone model Nanosized silicon carbide particles Composite materials Micromachining

Relationship between pore structure and hydration activity of CaO from carbide slag

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Chinese Journal of Chemical Engineering 2019年第11期27卷 2771-2782页

作者： Junqiang Zhang Shu Zhang Mei Zhong ZhiWang Guoyu Qian Junhao Liu Xuzhong Gong Key Laboratory of Green Process and Engineering National Engineering Laboratory for Hydrometallurgical Cleaner Production TechnologyInstitute of Process EngineeringChinese Academy of SciencesBeijing 100190China College of Materials Science and Engineering Nanjing Forestry UniversityNanjing 210037China Key Laboratory of Coal Clean Conversion&Chemical Engineering Process(Xinjiang Uyghur Autonomous Region) College of Chemistry and Chemical EngineeringXinjiang UniversityUrumqi 830046China University of Chinese Academy of Sciences Beijing 100190China

CaO needs to show high activity to be used as Ca-sorbent and slagging agent. Hydration activity is an important characteristic to evaluate the activity of CaO. In this study, carbide slag from polyvinyl chloride(PVC) industry was utilized as precursor for preparing high activity CaO. The roles of crystallite grain, average pore diameter(APD) and volume fraction of pore b 200 nm in diameter(VF200) in hydration activity of CaO from carbide slag(CS-CaO)were respectively investigated. The hydrolysis kinetics model of CaO shows a three-dimensional spherically symmetric diffusion model(D4), which suggests that hydration activity was mainly associated with APD and VF200 of CS-CaO with limited correlation to the crystal size. Specifically, the hydration activity of CS-CaO is increased with increasing VF200, while decreased with increasing APD. Under the invariable calcination temperature,the core–shell structure formed by the addition of graphite or Ca CO3 to CS effectively inhibits the sintering of CS-CaO and improves VF200. Consequently, the hydration activity of CS-CaO increased from 22.79 ℃·min^-1 to27.19 ℃·min^-1 and to 29.27 ℃·min^-1, with addition of 5% graphite or 5% CaCO3 into carbide slag, respectively.

关键词： carbide slag CaO Hydration activity Sintering Pore volume fraction

Experimental study on the tribo-chemical smoothening process between self-mated silicon carbide in a water-lubricated surfacecontact reciprocating test

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Friction 2019年第2期7卷 181-191页

作者： Le JIN Herbert SCHEERER Georg ANDERSOHN Matthias OECHSNER Dieter HELLMANN Center for Structural Materials Technische Universit?t Darmstadt KSB

Silicon carbide(SiC) can be tribo-chemically smoothened during a self-mated sliding procedure in the aqueous environment. As well reported in the point-contact tests, this smoothening process works well due to the abundant water as oxidant. After this smoothening process, the tribo-surface is well polished, a closely mated tribo-gap naturally forms, and an ultra-low friction state is built. However, water in the tribo-gap could be insufficient in industrial applications, e.g., the seal gap in mechanical seals. In this study, the tribo-chemical smoothening behavior in such environment was researched. A surface-contact reciprocating test was used to simulate the aqueous environment where water was insufficient. After tests, compared to the published results from the point-contact tests, the same ultra-low friction state was achieved. A part of the tribo-surface was tribo-chemically smoothened. The obtained smoothened surface microstructure was consistent with the published information. Meanwhile, severe abrasive wear occurred. A porous oxygen-rich layer was found existing beneath the abrasion-induced grooves, in which numerous smashed wear debris adhered on the worn surfaces. We concluded that the shortage of water initiated the severe abrasion, meanwhile the generated wear debris aggravated the wear condition. This understanding is instructive for developing new methods to avoid the severe abrasion in the same water insufficient environment.

关键词： silicon carbide surface-contact sliding friction tribo-chemical smoothening abrasion ultra-low friction mechanical seal