A novel binder and binder extraction method for powder injection molding of tungsten cemented carbide

An improved wax based multi component binder and a new debinding method termed high pressure condensed solvent extraction were developed for powder injection molding of tungsten cemented carbide. The results indicate that a critical powder loading of 65% (volume fraction) and an ideal rheological properties were obtained by the feedstock based on the binder. High debinding rate and specimens with high strength were obtained by the debinding method. Moreover, by making high temperature holding time adjustable, it makes the subsequent thermal degradation process more flexible to debinding atmosphere and carbon content of the as debinded specimens controllable. The transverse rupture strength, hardness and density of the as sintered specimens made by an optimized PIM process are 2.48 GPa, HRA90 and 14.72 g/cm 3, respectively. Good shape retention and about 0.02% dimension deviation were achieved.

Research on Ultrafine WC-10Co Cemented Carbide with High Propertie

WC- 10Co nanocomposite powder produced by spray pyrolysis-continuoas reduction and carbonization technology was used, and the vacuum sinteriag plus sinterhip process was cdopted to prepare ultrafine WCCo cemented carbide. The microstructure, grain size, porosity, density, Rockwell A hardness （ HRA ）, transverse rupture strength （ TRS ） , saturated magnetization and coercivity force were studied. The experimental results show that average grain size of the sample prepared by vacuum sintering plas sinterhip technology was about 420 nm, transverse rupture strength was more than 3460 MPa, and Rockwell A hardness of sintered specimen was more than 92.5. Ultrafine WC- 10Co cemented carbide with high strength and high hardness is obtained.

Mierostrueture and Properties of Coating from Cemented Carbide on Surface of Hl3 Steel

The microstructures and properties of coating from cemented carbide on the substrate of H 13 by vacuum powder sintering were studied. The effect of sintering temperature on the microstructures of coating was discussed. The interface characteristics between coating and H 13 steel substrate, microhardness distribution and wear resistance in the coating were analyzed. The coating from cemented carbide with thickness of 1-3 mm by vacuum powder sintering at temperature ranging from 1280℃to 1300 ℃ was obtained. The experimental results indicated that the coating with microhardness of HV 1600 favorable to wear resistance is strongly bonded with the H 13 steel substrate by mutual diffusion and penetration of Fe,Cr, Mo,V in substrate towards the coating and W, Co,Ni in coating towards the substrate.

Research on Ultrafine Tungsten Carbide-Cobalt(WC-Co) Cemented Carbide Rods of Miniature Drills for Highly Integrated Printed Circuit Board(PCB)

Nanocrystalline tungsten carbide-cobalt (WC-Co) composite powders produced through spray thermal decomposition-continuous reduction and carburization technology were used to prepare φ3.25 mm×38 mm ultrafine tungsten carbide-cobalt (WC-Co) cemented carbide rods through vacuum sintering plus sinterhip technology. The microstructure, Vickers hardness, density and Rockwell A hardness (HRA), transverse rupture strength (TRS), saturated magnetization and coercivity force were tested. The results show that the average grain size of the sintering body prepared through vacuum sintering plus sinterhip technology was 430 nm; transverse rupture strength (TRS) was 3850 MPa; Vickers hardness was 1890 and Rockwell A hardness of sintering body was 93. High strength and high hardness ultrafine WC-Co cemented carbide rods used to manufacture printed circuit board (PCB) drills were obtained.

再生微粉-电石渣制备硅酸盐水泥熟料及其水化性能研究

以再生微粉(RCP)和电石渣(CCS)等典型固废作为原材料,开展了固废基低碳水泥熟料制备技术研究。试验分析了煅烧温度(1300℃、1350℃、1400℃和1450℃)以及CCS和RCP含量对熟料煅烧和矿相组成的影响,并研究了1400℃下制备的水泥熟料的水化特性与力学性能。结果表明,RCP的加入可以降低水泥熟料的烧成温度,适量的RCP(60%)作为水泥生料掺入会提高熟料的力学性能,有利于水泥的早期水化。这些工作有助于推进建筑垃圾的资源化利用,为水泥生产中钙硅质原料提供了替代方案。

WC–xVC复合粉的制备及高含量VC对WC–Co基硬质合金微观结构和力学性能的影响

采用两步碳热还原法合成了WC–xVC复合粉,并以此为原料通过真空烧结法制备了不同Co含量(6%和10%,质量分数)的WC–Co–VC硬质合金,研究了烧结温度(1420℃、1440℃和1460℃)对硬质合金致密化过程的影响,分析了Co和VC含量对WC晶粒尺寸以及硬质合金维氏硬度和断裂韧性的影响。结果表明,随着烧结温度的升高,合金的相对密度增大,当烧结温度为1460℃时,所有合金试样的相对密度均大于98.5%。此外,随着VC含量的增加,WC的平均晶粒尺寸减小,这导致样品的硬度提高,断裂韧性降低。当VC质量分数为6%时,WC–6Co硬质合金和WC–10Co硬质合金的硬度均达到最大值,分别为HV301941和HV301838。在烧结温度和VC含量一定的情况下,试样的断裂韧性随着Co含量的增加而增加,试样的硬度随着Co含量的增加而减小。

配碳方式对超细WC粉末性能的影响

为了改善超细WC粉末的性能,尤其是降低其压制压力,本文研究了配碳方式对超细WC粉末性能的影响。结果表明:碳黑类型、配碳器类型、配碳时间和晶粒长大抑制剂碳化铬的添加次序对WC粉末性能有显著影响;碳黑类型影响WC的总碳和氧含量,对粉末的压制压力没有明显影响;配碳器类型对WC总碳和氧含量没有明显影响,与卧式配碳器比较,立式配碳器制备的WC粒度较小,压制压力更大;配碳时间对总碳、氧含量、粒度都没有明显的影响,配碳时间过长会提高压制压力;碳化铬添加次序对总碳没有明显的影响,添加碳化铬会增加WC的氧含量,降低WC粉末的粒度,增加压制压力。

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

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.

PREPARING NANO-CRYSTALLINE La DOPED WC/Co POWDER BY HIGH ENERGY BALL MILLING

The La doped WC/Co powder was prepared by high energy ball milling. The changes of crystal structure, micrograph and defect of the powder were investigated by means of XRD (X-ray diffraction), SEM (scanning electron microscope) and DTA (differential thermal analysis). The results show that adding trace La element into carbides is effective to minish the grain size of WC/Co powder. The La doped carbides powder with grain size of 30nm can be obtained after 10h ball milling. The XRD peak of Co phase disappeared after 20h ball milling, which indicated solid solution (or secondary solid solution) of Co phase in WC phase. The La doped powder with grain size of 10nm is obtained after 30h ball milling. A peak of heat release at the temperature of 470℃ was emerged in DTA curve within the range of heating temperature, which showed that the crystal structure relaxation of the powder appeared in the process of high energy ball milling. After consolidated the La doped WC/Co alloy by high energy ball milling exhibits ultra-fine grain sizes and better mechanical properties.

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

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.

Rheologic behavior and PIM processing of WC-TiC-Co powder feedstock

An improved wax-based binder was developed for the powder injection molding (PIM) of WC-TiC-Co cemented carbides. The critical powder loading and the rheologic behavior of the feedstock were determined. It was found that the critical powder loading could achieve up to 62.5% (volume fraction) and the feedstock exhibited a pseudo-plastic flow behavior. The injection molding, debinding and sintering processes were studied. The dimension deviation of the sintered samples could be controlled in the range of ±0.2% with the optimized processing parameters and the mechanical properties were better than or equivalent to those of the same alloy made by conventional press-sintering process.

Rheologic behavior and PIM processing of WC-TiC-Co powder feedstock

An improved wax-based binder was developed for the powder injection molding(PIM) of WC-TiC-Co cemented carbides. The critical powder loading and the rheologic behavior of thefeedstock were determined. It was found that the critical powder loading could achieve up to 62.5percent (volume fraction) and the feedstock exhibited a pseudo-plastic flow behavior. The injectionmolding, debinding and sintering processes were studied. The dimension deviation of the sinteredsamples could be controlled in the range of + -0.2 percent with the optimized processing parametersand the mechanical properties were better than or equivalent to those of the same alloy made byconventional press-sintering process.

MICROSTRUCTURES OF ULTRAFINE WC POWDERS

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超粗晶WC-Co硬质合金制备技术及发展趋势

超粗晶硬质合金因其独特的组织特征,表现出良好的抗冲击性、耐磨性、抗热疲劳性等优势,在凿岩、冲压模具、热轧辊领域具有极大的发展潜力,在硬质合金领域备受关注。本文概述了超粗晶硬质合金的特点及增韧机理,介绍了目前粗颗粒WC原料粉末和超粗晶硬质合金的制备工艺,以及超粗晶硬质合金性能强化方法的探索情况,最后对超粗晶硬质合金的发展趋势提出了几点思考。

电感耦合等离子体原子发射光谱法测定羰基镍粉中16种杂质元素量

建立电感耦合等离子体原子发射光谱法测定羰基镍粉中砷、镉、铅、锌、锑、铋、锡、钴、铜、锰、镁、铝、铁、钙、钼、硅等杂质元素含量的方法。采用硝酸(3+2)溶解样品,考察了酸度对测定的影响,确定了各元素最佳的分析谱线。在标准溶液中,元素含量分别为0、0.025、0.1、0.5、1.0μg/mL时,十六种元素的强度与浓度呈现良好的线性关系,对应的相关系数均大于0.999。最终的加标回收率为94.0%~104.0%,相对标准偏差RSD<6.53%(n=7)。该方法有效的提升了羰基镍粉中多元素分析的效率,满足硬质合金生产工艺的要求。

混合料研磨球料比对WC-12%Co超细晶硬质合金组织与性能的影响

混合料研磨球料比不仅影响粉末的混合均匀性和颗粒细化程度,还对合金的晶粒尺寸、晶界特性以及相变行为有重要影响。为了探讨不同混合料研磨球料比对超细晶硬质合金的组织和性能的影响规律,本文选取5.6∶1、6.3∶1和8.3∶1等3种研磨球料比制备混合料,并采用相同的工艺制备了WC-12%Co超细晶硬质合金。通过SEM和EBSD表征试样合金的显微组织结构,并对其物理力学性能进行测试和分析。结果表明,随着球料比增大,合金样品的WC晶粒细化,Co相分布逐渐均匀化,合金的矫顽磁力明显提高;当球料比增大时,试样合金内部的粗晶和聚晶减少,(0001)晶面比例增加,内部组织趋于细化和均匀化,合金的硬度和抗弯强度提高。

(V,Cr,W)C复合粉末对WC-11Ni硬质合金微观组织及力学性能的影响

以Cr_(2)O_(3)、WO_(3)、V_(2)O_(5)和炭黑为原料,采用碳热还原法在1500℃下反应2 h制备了(V,Cr,W)C复合粉末。采用XRD和SEM对(V,Cr,W)C复合粉末的相成分和显微组织进行了表征,研究了复合粉末的添加方式及含量对WC-11Ni硬质合金组织及力学性能的影响。结果表明,添加(V,Cr,W)C复合粉末的合金力学性能获得了显著提升,其抗弯强度、维氏硬度以及断裂韧性比未添加复合粉末的试样分别提高了19.97%、19.61%、12.18%。同时,添加(V,Cr,W)C复合粉末的合金性能优于添加(V,Cr)C复合粉末和添加WC+Cr_(3)C_(2)混合粉末的合金试样。另外,随着(V,Cr,W)C复合粉末添加量的增加,合金的抗弯强度、维氏硬度及断裂韧性均呈先增大后减小的变化趋势;当(V,Cr,W)C复合粉末的添加量为0.6%时,合金的抗弯强度、维氏硬度和断裂韧性达到最大值,分别为2835 MPa、1671 MPa、15.1 MPa·m^(1/2)。

木粉配比对木塑复合材料切削性能的影响

为了研究不同木粉配比对木塑复合材料切削性能的影响,避免木塑复合材料加工过程中高能耗和加工质量差的问题,试验采用直齿圆柱铣削方式,以木粉含量、每齿进给量和切削深度为变量,研究不同木粉含量对木塑复合材料铣削的性能影响。在每齿进给量和切削深度相同的情况下,四种不同木粉配比的木塑复合材料切削力大小为:WPC(木粉55%)<WPC(木粉50%)<WPC(木粉40%)<WPC(木粉70%);四种不同木粉配比的木塑复合材料切削温度和表面粗糙度的大小为:WPC(木粉40%)<WPC(木粉50%)<WPC(木粉55%)<WPC(木粉70%)。在木塑复合材料的实际生产过程中,木粉含量较少时,高转速和高切削深度时工件表面质量最佳,可以选用的参数为切削深度1.5 mm和每齿进给量0.5 mm/Z,可以提高加工效率。木粉含量较多时,切削深度0.5 mm时,每齿进给量应在0.3 mm/Z以下才能满足加工质量的要求。

钴粉粒度和成分对亚微米晶WC-10Co硬质合金组织和性能的影响

研究了原料钴粉的粒度、成分对亚微米晶WC-10Co硬质合金物理力学性能的影响。结果表明:在烧结工艺相同的情况下,钴粉越细,其表面能越高,熔化温度越低,合金致密化的时间越长,同时钴蒸气挥发时间也相应增加;随着钴粉粒度减小,合金密度增大,硬度、矫顽磁力降低,抗弯强度先增大后减小,当钴粉粒度为0.73μm时达最大。钴粉中Cl含量也是影响硬质合金孔隙的重要因素之一,当Cl含量达到550×10^(-6)时,合金内部出现大量孔隙。为得到优异性能的亚微米晶硬质合金,需严格控制原材料成分,同时调整生产工艺,缩短球磨时间,降低烧结温度。以FSSS粒度为0.73μm、Cl含量为171×10^(-6)的钴粉制备的亚微米晶WC-10Co硬质合金抗弯强度达4231N/mm^(2),硬度达91.8HRA,密度达14.45g/cm3,矫顽磁力达19.1kA/m。

球磨工艺对细颗粒钨粉质量及硬质合金晶粒夹粗的影响

利用球磨机对细颗粒钨粉进行分散处理,研究球磨过程不同转速、不同时间对细颗粒钨粉粒度及团聚颗粒的影响。将球磨后的钨粉制备成碳化钨粉和硬质合金,通过合金金相组织的对比分析找到细颗粒钨粉球磨工艺与合金晶粒夹粗的关联性,为合金晶粒夹粗问题提供新的解决思路。结果表明:选用21 r/min、80 min的球磨工艺分散处理的钨粉团聚颗粒最少,制备的碳化钨粉生产的硬质合金WC晶粒大小均匀、无夹粗出现。