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Selection of Heat Treatment Process and Wear Mechanism of High Wear Resistant Cast Hot-Forging Die Steel

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Journal of Iron and Steel Research International 2012年第5期19卷 50-57页

作者： WEI min-xian WANG Shu-qi WANG Lan CUI Xiang-hong chen kang-min School of Materials Science and Engineering Jiangsu UniversityZhenjiang 212013JiangsuChina

Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50--300 N at 400℃ by a pin-on-disc high temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy （SEM）, X-ray diffraction （XRD） and energy dispersive spectroscopy （EDS） ; wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1 120 ℃, then decreased at up to 1 220 ℃. As for tempering temperature and microstructure, the wear resistance increased in following order： 700℃ （tempered sorbite）, 200 ℃ （tempered martensite）, 440 to 650 ℃ （tempered troostite）. An appropriate combination of hardness, toughness, microstructural thermal stability was re- quired for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1 120 ℃, quenched in oil, then tempered at 440 to 650℃ for 2 h.

关键词： cast hot-forging die steel heat treatment process high-temperature wear mechanism wear behavior microstructure

Effect of Alloying Elements on Thermal Wear of Cast Hot-Forging Die Steels

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Journal of Iron and Steel Research International 2006年第5期13卷 53-59页

作者： WANG Shu-qi chen kang-min CUI Xiang-hong JIANG Qi-chuan HONG Bian School of Materials Science and Engineering Jiangsu University Zhenjiang 212013 Jiangsu China School of Materials Science and Engineering Jilin University Changchun 130025 Jilin China

The effect of main alloying elements on thermal wear of cast hot-forging die steels was studied. The wear mechanism was discussed. The results show that alloying elements have significant influences on the thermal wear of cast hot-forging die steels. The wear rates decrease with an increase in chromium content from 3% to 4% and molybdenum content from 2% to 3%, respectively. With further increase of chromium and molybdenum contents, chromium slightly reduces the wear resistance and molybdenum severely deteriorates the wear resistance with high wear rate. Lower vanadium/carbon ratio （1.5-2.5） leads to a lower wear resistance with higher wear rate. With an increase in vanadium/carbon ratio, the wear resistance of the cast steel substantially increases. When vanadium/carbon ratio is 3, the wear rate reaches the lowest value. The predominant mechanism of thermal wear of cast hot-forging die steels are oxidation wear and fatigue delamination. The Fe2O3 and Fe3O4 or lumps of brittle wear debris are formed on the wear surface.

关键词： hot-forging die cast steel alloying element thermal wear mechanism

Complex Boronized Layer on the Hot-dip Aluminized Steels and Its Surface Performances

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材料热处理学报 2004年第5B期25卷 653-656页

作者： LUOXin-min LIDian-kai WANGLan chenkang-min JiangsuUniversity ZhenjiangJiangsuP.R.China

Plain carbon steels were dipped in molten aluminum bath at 720°C ±5°C and diffused for 1, 2.5 and 6 hours respectively and then boronized at 950°C for 6 hours. The oxidation, hot-corrosion and abrasion resistance behavior were examined. The experimental results showed the compounds of the aluminized layer, from the surface to the matrix, were composed of Fe2Al5 ( n -phase ) .. Fe3Al ( -phase ) and a phase. The microstructure of aluminized plus complex boronized were similar to that simplex boronized. The XRD analysis results indicated that there existed Fe2B> Fe2AlB2and Fe2Als in this kind of layer. The simplex aluminized layers still remained bright gray appearance when oxidized at 950°C, but complex boronized layer was not able to resist oxidization at the temperature. Both the layers of complex boronized and aluminized had the same anti-oxidization level in the circulative oxidization tests, and also good anti-corrosion ability in molten salt medium. Under dry abrasive conditions, wear resistance of complex boronized layer was superior to the aluminized layer.

关键词：热镀喷铝钢硼化热腐蚀磨损

Thermodynamic model for deoxidation of liquid steel considering strong metal-oxygen interaction in the quasichemical model framework

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International Journal of minerals,Metallurgy and Materials 2024年第5期31卷 988-1002页

作者： Yong-min Cho Youn-Bae kang Graduate Institute of Ferrous and Eco Materials Technology Pohang University of Science and TechnologyPohangKyungbuk37673Rep.of Korea N.EX.T Hub POSCO HoldingsPohangKyungbuk37673Rep.of Korea Department of Materials Science and Engineering Pohang University of Science and TechnologyPohangKyungbuk37673Rep.of Korea

Herein,a thermodynamic model aimed at describing deoxidation equilibria in liquid steel was *** model provides explicit forms of the activity coefficient of solutes in liquid steel,eliminating the need for the minimization of internal Gibbs energy preliminarily when solving deoxidation *** elimination of internal Gibbs energy minimization is particularly advantageous during the coupling of deoxidation equilibrium calculations with computationally intensive approaches,such as computational fluid *** model enables efficient calculations through direct embedment of the explicit forms of activity coefficient in the computing *** proposed thermodynamic model was developed using a quasichemical approach with two key approximations:random mixing of metallic elements(Fe and oxidizing metal) and strong nonrandom pairing of metal and oxygen as nearest *** these approximations,the quasichemical approach yielded the activity coefficients of solutes as explicit functions of composition and temperature without requiring the minimization of internal Gibbs energy or the coupling of separate *** model was successfully applied in the calculation of deoxidation equilibria of various elements(Al,B,C,Ca,Ce,Cr,La,Mg,Mn,Nb,Si,Ti,V,and Zr).The limitations of the model arising from these assumptions were also discussed.

关键词： deoxidation equilibria thermodynamics quasichemical approach computational fluid dynamics

Tackling the proton limit under industrial electrochemical CO_(2)reduction by a local proton shuttle

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Carbon Energy 2024年第4期6卷 233-243页

作者： Tianye Shao kang Yang Sheng chen min Zheng Ying Zhang Qiang Li Jingjing Duan MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringSchool of Chemistry and Chemical EngineeringNanjing University of Science and TechnologyNanjingChina School of Chemical Engineering and Advanced Materials The University of AdelaideAdelaideSouth AustraliaAustralia

Industrial CO_(2)electroreduction has received tremendous attentions for resolution of the current energy and environmental crisis,but its performance is greatly limited by mass transport at high current *** this work,an ion‐polymer‐modified gas‐diffusion electrode is used to tackle this proton *** is found that gas diffusion electrode‐Nafion shows an impressive performance of 75.2%Faradaic efficiency in multicarbon products at an industrial current density of 1.16 A/cm^(2).Significantly,in‐depth electrochemical characterizations combined with in situ Raman have been used to determine the full workflow of protons,and it is found that HCO_(3)^(−)acts as a proton pool near the reaction environment,and HCO_(3)^(−)and H_(3)O^(+)are local proton donors that interact with the proton shuttle−SO_(3)^(−)from *** rich proton hopping sites that decrease the activation energy,a“Grotthuss”mechanism for proton transport in the above system has been identified rather than the“Vehicle”mechanism with a higher energy ***,this work could be very useful in terms of the achievement of industrial CO_(2)reduction fundamentally and practically.

关键词： industrial CO_(2)electroreduction proton donor proton pool proton shuttle proton transport mechanism

Maximizing the scattering of multiwavelength phonons in novel biphasic high-entropy ZrCoSb-based half-Heusler alloys

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Journal of Materiomics 2024年第1期10卷 45-56页

作者： Rongchun chen Yu Yan Guangshu Li Ruonan min Huijun kang Enyu Guo Zongning chen Xiong Yang Tongmin Wang Key Laboratory of Solidification Control and Digital Preparation Technology(Liaoning Province) School of Materials Science and EngineeringDalian University of TechnologyDalian116024China Ningbo Institute of Dalian University of Technology Ningbo315000China

The thermoelectric(TE)performance of p-type ZrCoSb-based half-Heusler(HH)alloys has been improved tremendously in recent years;however,it remains challenging to find suitable n-type ZrCoSb-based HH alloys due to their high lattice thermal conductivity(κ_(L)).In this work,n-type Zr_(1−x)Ta_(x)Co_(1−x)Ni_(x)Sb HH alloys were firstly designed by multisite *** evolution of the Raman peak proved that alloy scattering,phonon softening,anharmonicity,entropy-driven disorder,and precipitates had a combined effect on decreasingκ_(L)by 46.7%compared to that of pristine ***,Hf_(0.75)Zr_(0.25)NiSn_(0.99)Sb_(0.01)was introduced into Zr_(0.88)Ta_(0.12)Co_(0.88)Ni_(0.12)Sb to further suppressκ_(L).Remarkably,the grain size of the biphasic HH alloys was refined by at least one order of magnitude.A biphasic high-entropy HH alloy with y=0.2 exhibited the minimumκ_(L)of∼2.44 W/(m·K)at 923 K,reducing by 67.7%compared to that of ***,(Zr_(0.88)Ta_(0.12)Co_(0.88)Ni_(0.12)Sb)_(0.9)(Hf_(0.75)Zr_(0.25)NiSn_(0.99)Sb_(0.01))_(0.1)exhibited the highest TE figure of merit(∼0.38)at 923 *** cooperation between the entropy and biphasic microstructure resulted in multiscale defects,refined grains,and biphasic interfaces,which maximized the scattering of the multiwavelength phonons in HH *** work provides a new strategy for further reducing the grain size andκ_(L)of medium-and high-entropy HH alloys.

关键词： Biphasic half-Heusler alloys Thermoelectric properties Entropy engineering Multiscale defects

Microstructure evolution and mechanical properties of brazing joint for ultra-thin-walled Inconel 718 considering grain size effect and brazing temperature

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Chinese Journal of Aeronautics 2024年第2期37卷 541-556页

作者： Rui ZHAO Yueshuai SONG Hui kang min WAN School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China Jiangxi Research Institute of Beihang University Jiangxi 330000China

The systematic investigation of the mechanical properties and microstructure evolution process of ultra-thin-walled Inconel 718 capillary brazing joints is of great significance because of the exceptionally high demands on its *** achieve this objective,this study investigates the impact of three distinct brazing temperatures and five typical grain sizes on the brazed joints’mechanical properties and microstructure evolution *** evolution analysis was conducted based on Electron Back Scatter Diffraction(EBSD),Scanning Electron Microscopy(SEM),X-Ray Diffraction(XRD),High-Resolution Transmission Electron Microscopy(HRTEM),and Focused Ion Beam(FIB).Besides,the mechanical properties and fracture behavior were studied based on the uniaxial tension tests and in-situ tension *** findings reveal that the brazing joint’s strength is higher for the fine-grain capillary than the coarse-grain one,primarily due to the formation of a dense branch structure composed of G-phase in the brazing *** effects of grain size,such as pinning and splitting,are amplified at higher brazing ***,micro-cracks initiate around brittle intermetallic compounds and propagate through the eutectic zone,leading to a cleavage fracture *** fracture stress of fine-grain specimens is higher than that of coarse-grain due to the complex micro-crack ***,this study contributes significantly to the literature by highlighting the crucial impact of grain size on the brazing properties of ultra-thin-walled Inconel 718 structures.

关键词： EYWORDS Ultra-thin-walled structure Brazing Inconel 718 Grain size effect Brazing temperature

Spatial construction of ultrasmall Pt-decorated 3D spinel oxidemodified N-doped graphene nanoarchitectures as high-efficiency methanol oxidation electrocatalysts

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Rare Metals 2024年第1期43卷 186-197页

作者： Qi Zhang min-min Yan Wen-Fa Du chen-Yu Yin Jian Zhang Lu Yang Yun-Qing kang Hai-Yan He Hua-Jie Huang College of Mechanics and Materials Hohai UniversityNanjing 210098China New Energy Technology Engineering Lab of Jiangsu Province College of ScienceNanjing University of Posts&Telecommunications(NUPT)Nanjing 210023China International Center for Materials Nanoarchitectonics(WPIMANA) National Institute for Materials ScienceTsukuba 305-0044IbarakiJapan

Direct methanol fuel cell technology recently becomes the focus of both academic and engineering circles,which stimulates the exploitation and utilization of advanced electrode catalysts with high activity and long ***,we demonstrate a robust bottom-up approach to the spatial construction of three-dimensional(3D) spinel manganese-cobalt oxide-modified N-doped graphene nanoarchitectures decorated with ultrasmall Pt nanoparticles(Pt/MnCo_(2)O_(4)-NG) via a controllable selfassembly *** incorporation of MnCo_(2)O_(4)nanocrystals provides abundant hydroxyl sources to promote the oxidative removal of CO-like byproducts on Pt sites,while the existence of 3D porous N-doped graphene networks facilitates the transportation of both ions and electrons in the hybrid system,thus giving rise to remarkable synergetic coupling effects during the methanol oxidation ***,the optimized Pt/MnCo_(2)O_(4)-NG nano architecture expres ses exceptional electrocatalytic properties with a large electrochemically active surface area of 99.5 m^(2)·g^(-1),a high mass activity of1508.3 mA·mg^(-1),strong toxicity resistance and reliable long-term durability,which have obvious competitive advantages over those of conventional Pt/carbon black,Pt/carbon nano tube,Pt/graphene,and Pt/N-doped graphene catalysts with the same Pt usage.

关键词： Platinum MnCo_(2)O_(4) 3D graphene Electrocatalysts Methanol oxidation

Tungsten pnictides for water electrolysis:advances and perspectives

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Tungsten 2024年第4期6卷 675-695页

作者： Xue kang Xi-Han Tan Ning Han Jian-Feng Hou chen-min Yao Zhi-Jie chen Bing-Jie Ni Department of Chemistry and Chemical Engineering Lyuliang University Department of Materials Engineering State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration Key Laboratory of Oral Biomedicine Ministry of Education Hubei Key Laboratory of Stomatology School & Hospital of Stomatology Wuhan University School of Civil and Environmental Engineering The University of New South Wales

Hydrogen fuel is recognized as a promising energy carrier for the sustainable development of global energy system and the green hydrogen production via water electrolysis attracts great *** development of cost-effective electrocatalysts for water electrolysis is important for enhancing green hydrogen production ***,tungsten pnictides(phosphides and nitrides) have emerged as promising catalysts for water electrolysis,and efficient tungsten pnictide-based catalysts with different nanostructures,compositions,and surface chemical properties have been *** this review,recent progress in the design of tungsten pnictide-based electrocatalysts for water electrolysis is comprehensively *** synthesis of tungsten pnictide-based electrocatalysts are discussed ***,current achievements in developing efficient tungsten pnictide electrocatalysts for water electrolysis are detailed,and four key catalyst design strategies(i.e.,nanostructure control,heteroatom doping,defect engineering,and heterostructure design) are *** physicochemical properties-catalytic performance relationship of tungsten pnictide-based electrocatalysts is also *** last,perspectives in this field are put forward for guiding further research on the design and application of high-performance tungsten pnictide-based electrocatalysts.

关键词： Electrocatalysts Hydrogen evolution reaction Oxygen evolution reaction Tungsten nitrides Tungsten phosphides