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Microstructure and mechanical properties of WC-(Ti,M)(C,N)-Co Cemented carbides with different nitrogen contents

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Rare Metals 2022年第10期41卷 3530-3538页

作者： Han-Jie Fan Ying Liu Jin-Wen Ye Wei-Bin Qiu Yu-Chong Qiu School of Materials Science and Engineering Sichuan UniversityChengdu610065China

Three kinds of(Ti,M)(C_(1-x),N_(x))(M=Ta,Nb,W) quaternary solid-solution powders with various nitrogen contents were synthesized by carbothermal reductionnitridation(CRN) process.Effect of nitrogen content on the microstructure and mechanical properties of WC-(Ti,M)(C_(1-x),N_(x))-Co Cemented carbides fabricated by sinterhot isostatic pressing(HIP) were systematically investigated in this paper.The results show that the nitrogen content in the carbonitride raw powders strongly influences the morphology,the grain size and the compositions of the Cemented carbides.All the Cemented carbides with different nitrogen contents have a similar microstructural appearance:weak core-rim structure consisting of solidsolution phase embedded in WC-Co system.It is also observed that the carbonitride solid solution could somewhat reduce the WC grain growth,and the effectiveness of refining and the rim thickness are sensitively related to the nitrogen content of(Ti,M)(C_(1-x),N_(x)) solid solutions.In addition,with an increase in the nitrogen content,mechanical properties of these hard metals are enhanced,which were discussed in terms of the constituent,the microstructure and the solution behavior of the carbonitride solid solutions.

关键词： Cemented carbides Solid-solution powders Nitrogen content Mechanical properties

Change in relative density of WC-Co Cemented carbides in spark plasma sintering process

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Rare Metals 2008年第1期27卷 74-77页

作者： SUN Lan LIN Chenguang JIA Chengchang JIA Xian XIAN Mina School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China School of Manufacturing Science and Engineering Sichuan University Chengdu 610065 China Powder Metallurgy and Special Materials Department General Research Institute for Nonferrous Metals Beijing 100088 China

The relative density of WC-Co Cemented carbides during spark plasma sintering（SPS） was analyzed.Based on the change in displacement of the ram in the SPS system,the relative densities in the sintering process can be achieved at different temperatures.The results indicated that densification of the samples started at near 900°C,the density rapidly reached its maximum at the increasing temperature stage,in which the temperature was lower than the sintering temperature of 1200°C,and most of the densification took place in the stage.Besides,the theoretical values were consistent with the experimental results.

关键词： spark plasma sintering relative density WC-Co Cemented carbides

Microstructure and mechanical properties improvements in Cemented carbides by(Cr,Mo,Ta)_(2)(C,N) inhibitors

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Rare Metals 2021年第3期40卷 679-686页

作者： Jie Tang Ying Liu Jin-Wen Ye Zhi-Nan Cao Shi-Qing Ma Xiao-Jiao Yang School of Materials Science and Engineering Sichuan UniversityChengdu 610065China Key Laboratory of Advanced Special Material and Technology Ministry of EducationChengdu 610065China

Grain growth inhibitors can effectively suppress the grain size of tungsten carbide(WC),and consequently improve the hardness and strength of the Cemented carbides;however,the toughness,one of the most important properties,usually deteriorates with inhibitors.Here,(Cr,Mo,Ta)_(2)(C,N) synthesized by carbothermal reductionnitridation was used as a novel inhibitor,and its effects on the microstructure and mechanical properties of the Cemented carbides were investigated.The results showed that the Cemented carbides containing(Cr,Mo,Ta)_(2)(C,N)outperformed its counterpart comprising the traditional inhibitors in comprehensive mechanical properties,which was mainly attributed to the better inhibition performance provided by the(Cr,Mo,Ta)_(2)(C,N) solid-solution powders.With the content of(Cr,Mo,Ta)_(2)(C,N) increasing from 0 wt% to 1.25 wt%,the average grain size of WC in the Cemented carbides decreased from 0.85 to 0.60 μm firstly,and then increased to 0.64 μm.With 1.00 wt%(Cr,Mo,-Ta)_(2)(C,N) addition,the Cemented carbides with the best performance of hardness(HV_(30)) of 15.55 GPa,transverse rupture strength of 4272 MPa,fracture toughness of13.91 MPa·m1/2 were obtained.The electron backscattered diffraction(EBSD) measurements showed that Cemented carbides with(Cr,Mo,Ta)_(2)(C,N) processed more amount of∑2 boundary compared with the other specimens,which contributed to better fracture resistance.

关键词： Cemented carbides Microstructure Mechanical properties (Cr,Mo,Ta)_(2)(C,N) Electron backscattered diffraction(EBSD)

Effect of Carbon Addition on Microstructure and Properties of WC-Co Cemented carbides

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Journal of Materials Science & Technology 2012年第9期28卷 837-843页

作者： Chongbin Wei Xiaoyan Song Jun Fu Xiaosen Lv Haibin Wang Yang Cao ShixianZhao Xuemei Liu College of Materials Science and Engineering Key Lab of Advanced Functional MaterialsEducation Ministry of ChinaBeijing University of TechnologyBeijing 100124China Beijing Belying Hardalloy Co. Ltd.Beijing 100055China

Based on a unique method to synthesize WC-Co composite powder by in-situ reactions of metal oxides and carbon, the effects of the carbon addition in the initial powders on the phase constitution, microstructure and mechanical properties of the Cemented carbides were investigated. It is found that with a suitable carbon addition the pure phase constitution can be obtained in the sintered bulk from the composite powder. The mechanical properties of the Cemented carbides depend on the phase constitution and the WC grain structure. To obtain the excellent properties of the WC-Co bulk, it is important to obtain the pure phase constitution from the appropriate carbon addition in the initial powders and a suitable grain size.

关键词： Cemented carbides Carbon addition Composite powder Phase constitution Mechanical property

Growth kinetics of cubic carbide free layers in graded Cemented carbides

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International Journal of Minerals,Metallurgy and Materials 2012年第1期19卷 64-71页

作者： Liu-yong Shi Yi-min Liu Ji-hua Huang Shou-quan Zhang Xing-ke Zhao School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China College of Mechanical and Electrical engineering Hainen University Danzhou 571737 China Xiarnen Golden Egret Special Alloy Co. Ltd. Xiamen 361006 China

In order to reveal the formation mechanism of cubic carbide free layers （CCFL）, graded Cemented carbides with CCFL in the surface zone were fabricated by a one-step sintering procedure in vacuum, and the analysis on microstructure and element distribution were performed by scanning electron microscopy （SEM） and electron probe micro-analyzer （EPMA）, respectively. A new physical model and ki- netic equation were established based on experimental results. Being different f^om previous models, this model suggests that nitrogen diffu- sion outward is only considered as an induction factor, and the diffusion of titanium through liquid phase plays a dominative role. The driving force of diffusion is expressed as the differential value between nitrogen partial pressure and nitrogen equilibrium pressure essentially. Simulation results by the kinetic equation are in good agreement with experimental values, and the effect of process parameters on the growth kinetics of CCFL can also be explained reasonably by the current model.

关键词： graded materials Cemented carbides diffusion kinetics

Properties and microstructure of VC/Cr_3C_2-doped WC/Co Cemented carbides

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Rare Metals 2007年第6期26卷 584-590页

作者： LEI Yiwen SUN Jing DU Xiwen ZHAI Qi HU Shengliang School of Mechanical and Electronic Engineering Tianjin Polytechnic University Tianjin 300160 China School of Material Science and Engineering Tianjin University Tianjin 300072 China

This paper deals with the effects of codoped VC/Cr3C2 and sintering temperature on the magnetic and mechanical properties of ultra-fine grained WC-12%Co alloys. Results show that the synergistic action of doped VC/Cr3C2 in optimal proportion enhances both the hardness and transverse rupture strength （TRS） of the alloys, with more homogeneous microstructtLre. When the alloy is sintered at 1430℃ and with 0.5% Cr3C2/0.2% VC, the TRS reaches 3786 MPa, the hardness is 91.7 HRA and the grain size smaller than 0.6 μm. The numerical analyses on grain growth during the sintering process show that both VC precipitating on the WC grain boundary and Cr3C2 dissolving in the Co phase decrease the solid/liquid interfacial energy γ, the process of dissolution and reprecipitation is greatly retarded and the coarsening of WC grains is inhibited.

关键词： grain growth inhibitor ultra-fine grain Cemented carbides microstructure transverse rupture strength （TRS）

Role of Co Content on Densification and Microstructure of WC–Co Cemented carbides Prepared by Selective Laser Melting

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Acta Metallurgica Sinica(English Letters) 2021年第9期34卷 1245-1254页

作者： Jinyang Liu Jian Chen Li Zhou Bingyao Liu Yang Lu Shanghua Wu Xin Deng Zhongliang Lu Zhipeng Xie Wei Liu Jianye Liu Zhi Qu School of Electromechanical Engineering Guangdong University of TechnologyGuangzhou 510006China School of Electromechanical Engineering Guangdong Polytechnic Normal UniversityGuangzhou 510635China Master Group(Guangdong)Technology Research Co LtdYunfu 527400China State Key Laboratory for Manufacturing Systems Engineering Xi’an Jiaotong UniversityXi’an 710049China Guangdong Xi’an Jiaotong University Academy Foshan 528300China State Key Laboratory of New Ceramics and Fine Processing Tsinghua UniversityBeijing 100091China Guangdong Hanbang 3D Technology Co. LtdZhongshan 528427China Guangdong Fenghua Zhuoli Technology Co. LtdFoshan 528225China

WC–Co Cemented carbides, well-known as the conventional tooling materials, have not been successfully produced by one step additive manufacturing processes such as selective laser melting(SLM) yet. The microstructure evolution as well as WC grain growth behavior has rarely been investigated in detail during SLM process. In this study, the WC–Co Cemented carbides with different Co contents(12–32 wt%) were prepared by optimized SLM processes for comparative investigation of densification behavior, microstructure characterization and mechanical property. The increase in Co content in feedstock carbide granules can improve the densification behavior during SLM process. The SLM processed WC-12 Co shows larger average WC grain size and higher percentage of coarser WC grains as compared with both WC-20 Co and WC-32 Co. The microstructure characterization, combined with finite element simulation, shows the WC grain growth mechanisms include agglomeration and dissolution-deposition of WC during SLM process and agglomeration of WC is an important mechanism especially for WC–Co Cemented carbides with Co content as low as 12 wt%. The comparison between horizontal(perpendicular to the SLM laser beam) and vertical(parallel to the SLM laser beam) cross sections of carbides shows that SLM process introduces a certain degree of microstructure and mechanical behavior anisotropy for WC-12 Co, WC-20 Co, and WC-32 Co.

关键词： Cemented carbides Selective laser melting Microstructure Densifi cation behavior Finite element simulation

Sintering characteristics and microstructure of WC-Co-VC/Cr_3C_2 ultrafine Cemented carbides

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Rare Metals 2009年第5期28卷 482-486页

作者： LEI Yiwen WU Enxi School of Mechanical and Electronic Engineering Tianjin Polytechnic University Tianjin 300160 China State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China

The sintering characteristics, microstructure, and mechanical properties of ultrafine WC-12%Co-0.2%VC/0.5%Cr3C2 Cemented carbides were investigated. Dilatometric and differential thermal analyses （DTA） indicate that the compacts start to shrink at 600°C, the shrinkage rate peak is at 1190°C, and the liquid formation temperature is lower than the W-C-Co eutectic temperature （1330°C）. Microstructure analysis results show that the Cemented carbides with fine and homogeneous microstructure were obtained when sintered at 1430°C. Continuous and discontinuous grain growth was suppressed due to the synergistic action of VC/Cr3C2. The transverse rupture strength （TRS） of the samples reaches 4286 MPa, with the hardness HRA 92.1. The fine and homogeneous microstructure, alloy strengthening, and different phase constitutions of binder in the Cemented carbides result in high hardness and TRS. Continuous and discontinuous grain growth was observed in the cemented carbide sintered at 1450°C, which results in significant decreases of hardness and TRS. It indicates that VC/Cr3C2 additions in the Cemented carbides can only suppress the grain growth at a certain temperature.

关键词： Cemented carbides sintering characteristic grain growth microstructure mechanical properties

Effects of Phosphorus Additions on Microwave Sintering Properties of Uitrafine WC-10Co Cemented carbides

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Journal of Wuhan University of Technology(Materials Science) 2007年第4期22卷 725-727页

作者：全峰周建 State Key Lab of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology State Key Lab of Advanced Technology for Materials Synthesis and Processing Wohan University of Technology

Using the microwave sintering technology, the effects of phosphorus （P） additions on the microstructure and properties of the ultrafine WC-10Co alloys were investigated. The experimental results show that with only 0.3wt% P additions, full density WC-10Co cermets were obtained at temperature of 1250℃, which is 70 ℃ lower than that of the undoped counterparts. Lower sintering temperature can result in finer WC grain growth; therefore, the P-doped WC-10Co alloys exhibited higher hardness than the undoped ones. But at the same time, P doping could lead to sacrifice of fracture toughness ofWC-10Co Cemented carbides.

关键词： microwave sintering Cemented carbides ultrafine hardmetals phosphorus grain growth inhibitor