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Effect of furnace atmosphere on sintering process of chromium-containing steel via powder metallurgy

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Journal of Iron and Steel Research International 2021年第7期28卷 889-900页

作者： Zhao-qiang Tan Ulf EngstrÖm Kun Li Yong Liu State Key Laboratory of powder metallurgy Central South UniversityChangsha 410083HunanChina HÖganäs China co. Ltd.Shanghai 201799China

During a powder metallurgy process such as sintering,the primary role played by the atmosphere in furnace is to prevent an excessive oxidation of powder compacts in case of the formation of oxides as residuals on powder *** particular,the adjustment of furnace atmosphere is the key to eliminate the phenomenon"decarburization"likely to occur in carbon-containing compacts.A continuous belt furnace was used to stabilize the potentials of carbon and oxygen in zones divided by sintering,delubrication,and *** and manganese,which are sensitive to oxygen,were added to improve mechanical properties in a cost-effective *** of steel containing chromium were sintered in an atmosphere composed of co,O_(2),and H_(2).The effects of atmosphere,lubricant,and graphite on oxidation(or reduction)and decarburization(or carburization)were *** quality was achieved under the control of delubrication *** is indicated that in a protective atmosphere,the chemical reactions occurring at various stages took remarkable effect on the quality of sintered *** potentials of oxygen and carbon in a continuous belt furnace were monitored and analyzed using an on-line thermal measuring unit consisting of thermocouple,oxygen probe,and carbon monoxide *** avoidance of oxidation and decarburization promises desired micro structure and carbon content and satisfactory properties through the adjustment of technical parameters,e.g.,the composition of gases in delubrication and various sintering zones,the rate of gas inlet,and cooling rate.

关键词： powder metallurgy steel Sintering atmosphere Carbon potential Oxygen partial pressure Chromium alloy

Micro-analysis of high-temperature oxidation-resistance of a new kind of heat-resistant grid plate in grate-kiln

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International Journal of Minerals,metallurgy and Materials 2009年第6期16卷 632-639页

作者： Jun-you Liu Feng Li Jie Liu Yi Zhang Yu-lei Wang School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China beijing BKDR metallurgy Engineering ＆ Technology co. ltd. Beijing 100083 China

To further improve the oxidation-resistance of materials and reduce the cost of grid plates in grate-kiln, a new kind of heat-resistant grid plate was developed. The microstructure of this grid plate with a life more than 18 months was studied by XRD, SEM and EDS techniques. The results show that high hardness, high intensity and good impact property make the new kind of heat-resistant grid plate and its oxide film have a higher resistance to deformation and abrasion at 900-1000℃ Besides, small grain size is beneficial to form a complete protective oxide film. The oxide film composed of SiO2 layer, Cr2O3 layer and Fe2O3 layer is rather thin and bonds closely with the backing. The forming of the chemical stable nickel-rich layer increases the density of Cr2O3 layer.

关键词： grate-kiln process grid plate heat resistance high-temperature oxidation-resistance oxide film

Spark plasma sintering of high-toughness ZrO_2 materials doped with yttrium

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Rare Metals 2008年第5期27卷 479-483页

作者： CHEN Liliang JIA Chengchang WANG Kaiming nstitute of powder metallurgy School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Department of Physics University of Science and Technology Liaoning Anshan 114051 China

Zirconia powders doped with yttrium prepared by special liquid-phase precipitation method were sintered by spark plasma sintering （SPS） to obtain high performance samples. The microstructure, phase composition, and mechanical properties of the samples were studied. The results of X-ray diffraction （XRD）, Raman spectrum, and transmission electron microscope （TEM） show that the phase is tetragonal. The powders with large surface area and high sintering activity, due to small crystallite size, could be densified at 1100℃. The highest relative density of the sample obtained at 1300℃ is higher than 99% （the tetragonal phase is 6.08 g/cm^3）. The Hv and KIC are 13.76 GPa and 15.4 MPa.m^1/2, respectively.

关键词： zirconia tetragonal phase spark plasma sintering nanopowders

Effect of Additive Cu-10Sn Alloy on Sintering Behavior of Elemental powders in composition of 465 Stainless Steel

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Journal of Iron and Steel Research International 2007年第4期14卷 61-64,74页

作者： Farid Akhtar Department of Metallurgical and Materials Engineering University of Engineering and TechnologyLahore 54890PakistanInstitute of Powder MetallurgyUniversity of Science and Technology BeijingBeijing 100083China

The addition of Cu-10Sn alloy for developing the high strength 465 maraging stainless steel from elemental powders was studied. The sintering parameters investigated include the sintering temperature, the sintering time, and the mass percent of Cu-10Sn. For vacuum sintering, effective sintering occurs at temperature between 1 250 ℃ and 1 300 ℃. The maximum sintered density was achieved at 1 300 ℃ for 60 min with 3% （in mass percent） Cu- 10Sn alloy. More than 3% （in mass percent） Cu-10Sn content and temperature above 1 300 ℃ caused slumping of the samples. A maximum density of 7.4 g/cm^3 was achieved with 3% （in mass percent） Cu-10Sn content at a sintering temperature of 1 300 ＂C for 60 rain. A maximum ultimate tensile strength （UTS） of 517 MPa was achieved with 3% （in mass percent） Cu-10Sn content. With content higher than 2% （in mass percent） Cu-10Sn, a maximum increase in the density was observed. The fracture morphologies of the sintered samples are also reported.

关键词： 465 maraging stainless steel sintering UTS Cu-10Sn alloy

Fabrication of commercial pure Ti by selective laser melting using hydride-dehydride titanium powders treated by ball milling

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Journal of Materials Science & Technology 2019年第2期35卷 322-327页

作者： Wei Xu Shiqi Xiao Xin Lu Gang Chen Chengcheng Liu Xuanhui Qu beijing Advanced Innovation Center for Materials Genome Engineering Institute for Advanced Materials and Technology University of Science and Technology Beijing beijing Key Laboratory for Advanced powder metallurgy and Particulate Materials beijing Laboratory of Metallic Materials and Processing for Modern Transportation

Micro-fine sphericalpowders are recommended for selective laser melting(SLM). However, they are mostly expensive due to the complex manufacturing technique and low yield. In this paper, using lowcost treated hydride-dehydride(HDH) Ti powders, commercial pure Ti(CP-Ti) was successfully fabricated by SLM. After 4-h milling, the resulting powders become near-spherical with no obvious angularity, and have optimal flowability with the apparent density of 1.64 ± 0.02 g/cm^3, tap density of 2.10 ± 0.04 g/cm^3,angle of repose 40.11?±0.09?, and Carr's index of 77.74 ± 0.15. The microstructure was determined with full acicular martensitic β phase. The CP-Ti can achieve superior mechanical properties with the ultimate tensile strength of 876.1 ± 20.5 MPa and elongation of(14.7 ± 0.5)%, which exhibit distinctly competitive compared to the as-cast CP-Ti or Ti-6 Al-4 V. Excellent mechanical properties together with its low-cost make SLM-fabricated CP-Ti from modified HDH Ti powders show promising applications.

关键词： Selective laser melting Hydride-dehydride powders Titanium Microstructure Mechanical properties

Influence of fabricating process on microstructure and properties of spheroidal cast tungsten carbide powder

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中国有色金属学会会刊：英文版 2005年第2期15卷 270-274页

作者：戴煜谭兴龙李玉玺羊建高黄伯云 State Key Laboratory of powder metallurgy Central South University Changsha 410083 China Hunan Denli New Materials Engineering Center co.ltd Changsha 410083 China

A super-high temperature furnace was developed to fabricate spheroidal cast tungsten carbide powder with excellent flowability and fine feathery structure in a large scale. Optical microscope and scanning electron microscope were taken to characterize the morphology and microstructure of cast tungsten carbide powder. X-ray diffractometry was used to analyze the phase composition of powders involved. It is found that the carbon potential in the furnace and feeding speed play an important role on the microstructure, morphology and properties of the spheroidal cast tungsten carbide powder. As carbon potential is between 0.3% and 0.9% in the furnace, cast tungsten carbide powder with hardness over 2800(HV0.5), flowability over 7.1 s/50 g and tap density over 10.3 g/cm3 is obtained.

关键词：精细羽状结构超高温炉工艺参数流动性球状碳化钨熔炼

Densification behavior of high Nb containing TiAl alloys through reactive hot pressing

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Journal of University of Science and Technology beijing 2007年第3期14卷 251-255页

作者： Yanhang Wang Junpin Lin Yuehui He Yanli Wang Guoliang Chen State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China State Key Laboratory for powder metallurgy Central South University Changsha 410083 China

Densification behavior of high Nb containing TiAl alloys through reactive hot pressing was investigated. The results showed that the density of the sample hot pressed at 1400°C could reach a near full density of 98.37%. However, the densification abnormality was observed at 1500°C. The diffusion of elemental Nb during microstructural evolution is an important aspect affecting densification, which will form pore nests. With the increase of hot pressing temperature, the diffusion of Nb becomes more adequate. HIP （Hot isostatic pressing） treatment can only decrease porosity to some extent, but cannot eliminate it completely.

关键词： TiAl based alloy powder metallurgy densification hot pressing

Effect of helium implantation on SiC and graphite

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Chinese Physics B 2015年第3期24卷 394-397页

作者：郭洪燕葛昌纯夏敏郭立平陈济鸿燕青芝 Institute of powder metallurgy and Advanced Ceramics Southwest Jiaotong University Institute of Nuclear Materials University of Science and Technology Beijing School of Physics and Technology Wuhan University

Effects of helium implantation on silicon carbide（SiC） and graphite were studied to reveal the possibility of SiC replacing graphite as plasma facing materials. Pressureless sintered SiC and graphite SMF-800 were implanted with He＋ions of 20 ke V and 100 ke V at different temperatures and different fluences. The He^＋ irradiation induced microstructure changes were studied by field-emission scanning electron microscopy（FESEM）, atomic force microscopy（AFM）, and transmission electron microscopy（TEM）.

关键词： plasma facing materials SiC irradiation damage fusion reactor

Permanent magnetic properties of Nd-Fe-B melt-spun ribbons with Y substitution

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Rare Metals 2020年第1期39卷 55-61页

作者： Cao-Huan Zhang Yang Luo Dun-Bo Yu Ning-Tao Quan Gui-Yong Wu Ya-Kun Dou Zhou Hu Zi-Long Wang National Engineering Research Center for Rare Earth Materials General Research Institute for Nonferrous MetalsBeijing100088China Grirem Advanced Materials co.ltd Beijing100088China

Phase constituents,microstructures and magnetic properties of melt-spun Nd12-xYxFe81B6 Nb ribbons were investigated *** influence of Y substitution for Nd on the phase stability,grain size and magnetic exchange coupling was *** is found that all the ribbons crystallize in the tetragonal 2:14:1 structure,i.e.,with single hard magnetic phase at the roll speed of25 m *** the increase in Y doping,Curie temperature(Tc)increases,while the coercivity decreases monoclinic ***,remanence magnetization(Br)and maximum energy product((BH)max)fluctuate and the maximum value is obtained at certain amount of *** optimum magnetic properties of intrinsic coercivity of intrinsic coercivity(Hcj)=908.2 kA·m-1 and(BH)max=118.52 kJ·m-3 are achieved when x=*** can be attributed to the strengthened exchange coupling between the neighboring nanograins in Nd-Y-Fe-B meltspun powder based on the Henkel ***,Y substitution also significantly improves the temperature stability of magnetic *** coercivity temperature coefficient ofβ=-0.157%·℃-1 and remanence temperature coefficient ofα=-0.32%·℃-1 are gained,which are greatly reduced compared with those of the undoped Nd-Fe-B compounds.

关键词： Rapid quenching (Nd,Y)-Fe-B alloy Exchange coupling Thermal stability