球形粉末多孔钛的性能与粉末粒度和烧结制度的关系

以等离子旋转电极制取的TC4合金球形粉末为原料,经涂覆成形烧结工艺制备多孔试样,并系统地研究了多孔钛的性能与原始粉末粒度和烧结制度的关系。研究结果表明:在确定的工艺条件下,影响多孔钛孔径和透过性能的关键因素是原始粉末粒度;孔径与原始粉末粒度呈线性关系,即最大孔径值为原始粉末粒度的1/2—1/2.5,过滤精度值为原始粉末粒度的1/5—1/6;而透气性能随原始粉末粒度增加呈非线性迅速增加;孔隙度主要取决于粉末的堆积状态,由涂覆成形工艺制取的多孔钛,其孔隙度为40—43%;多孔钛的压缩强度主要与原始粉末粒度和烧结制度有关,并随原始粉末粒度的变小、烧结温度的提高及保温时间的延长而增加。     

增塑挤压-烧结制备多孔 Fe3Al过滤管

采用自制FeAl粉末与增塑剂的混合物,用增塑挤压-烧结法制备了多孔Fe3Al过滤管,研究了增塑剂和粉末粒度对过滤管组织和性能的影响.结果表明,合适的挤压料配比为5％～14％,挤压力为3～5 t;随烧结温度的升高,过滤管的烧结收缩率提高,最大孔径和相对透气系数呈先增大后降低的趋势;随增塑剂添加量的增多,过滤管的烧结收缩率、最大孔径和相对透气系数增大,而抗拉强度降低.采用粉末粒度为-500目的Fe3Al粉末配制挤压料,其过滤管的烧结收缩率和相对透气系数明显高于采用+500目Fe3Al粉末配比的挤压料.最佳配比参数为-500目的粉末、增塑剂添加量7％,烧结工艺为1250℃×3 h,此时多孔体的最大孔径为5.4 μm,相对透气系数为31.5 m3/(h·kPa· m2).     

粉轧工艺对多孔钛板性能的影响

众所周知,多孔材料的性能主要取决于粉末特性与粉末冶金工艺。作过滤材料使用的多孔钛板有三个主要性能:渗透性,过滤精度和拉伸强度。过滤精度取决于多孔板的最大孔径,后者与粉末粒度有关:d 最大=K_1D     

粉末冶金多孔材料的过滤性能与粉末粒度和烧结温度的关系

本文系统地叙述了用球形粉末颗粒制取的多孔材料的基本性能——过滤性能与原始粉末粒度、烧结温度的关系。研究表明,随着温度的提高,对于细粉末材料,其孔径与透过性能均显著下降;对于粗、中颗粒粉末材料,温度的影响不十分显著。随着温度的提高,材料的孔径分布峰值向粗孔径方向偏移。在确定的工艺条件下,原始粉末的粒度对材料的过滤性能起决定作用。用等静压成形烧结工艺制取的多孔材料,过滤精度与原始粉末粒度成直线关系,且二者的比值约为1/7,松装烧结工艺制取的多孔材料,二者的比值约为1/5。随着粉末粒度的增大,材料的透过系数非直线地迅速升高。透过性能主要取决于材料中粉末颗粒的堆积状况,松装烧结的多孔材料具有最佳的透过性能。本研究结果可作为制取多孔材料时正确选择原始粉末粒度与工艺参数的依据。     

多孔不锈钢通气锥/管在煤气化工程中的应用研究

在壳牌煤气化工程中,需要多孔不锈钢通气锥/管作为气体分布元件,以保证煤粉和飞灰的流态化连续输送.本研究针对使用要求,主要研究了粉末轧制和冷等静压技术制备的多孔不锈钢通气锥/管的渗透性能和强度.结果表明,冷等静压成形后经过烧结和复烧的通气锥/管,孔隙度在32%-35%范围,最大孔径为20μm,通气锥的整体耐压强度都大于2.5 MPa,符合壳牌煤气化技术流态化输送的要求.     

粉末冶金多孔材料

粉末冶金多孔材料,也称多孔烧结材料,由金属或合金粉末经成形、烧结工艺而制成。常用的金属或合金有青铜、不锈钢、铁、镍、钛、钨、钼以及难熔金属化合物等。粉末冶金多孔材料具有孔径和孔隙度均可控制、导热、导电、可焊接和加工、高的比强度、冲击韧性、能量吸收性能、化学活性、阻波性能、独特的光学性能、良好的透过性、选择性的渗透与吸附性、止振性能等一系列优异的性能。在气体和液体过滤、高温燃气的净化过滤、熔融金属的过滤、固体催化、缓冲器及吸震器、电极材料、屏蔽材料、流体分布装置、热交换器、加热器、散热器、结构材料、生物材料等领域得到广泛应用。     

气泡法分析烧结不锈钢纤维毡孔径分布

气泡法测量多孔材料的孔径分布是一种简单易行的方法,采用线性插值的方法解析气泡所测得的流量与压差曲线,可得到孔体积和孔数分布曲线.对不锈钢纤维毡的测试结果表明,该方法解析得到的孔径分布较真实地反映出金属纤维毡的孔结构状况,依孔体积分布峰值所对应的孔径值可近似确定这种过滤材料的过滤精度,其值偏差不超过±5.1%.     

镍基合金多孔管不同烧结温度下的孔结构和力学性能

以Inconel625合金粉末和增塑剂为原料,采用增塑挤压工艺成功制备出规格为Ф6 mm×600 mm的薄壁细长镍基合金多孔过滤管坯体。研究了烧结温度对过滤管孔结构和性能的影响。结果表明,随着烧结温度的提高,过滤管的烧结收缩率增大、拉伸断裂强度提高,最大孔径和相对透气系数则呈现逐渐降低的趋势。经1120℃×2 h真空烧结制得的镍基合金过滤管的最大孔径为1.42μm、相对透气系数为31.53 m~3/(h·k Pa·m~2),拉伸断裂强度为340.83 MPa。在该条件下得到的镍基合金过滤管具有良好力学性能,同时兼具适合的孔径和透气系数。     

成形压力对Fe16Al2Cr多孔材料性能的影响

以Fe16Al2Cr预合金粉末为原料,采用模压成形、真空烧结的方法制备了Fe16Al2Cr多孔材料,研究了粉末成形压力与Fe16Al2Cr多孔材料性能的关系。结果表明：小于31 μm的Fe16Al2Cr粉末的压制成形性能较差,压坯强度低;烧结过程中,厚度收缩远大于径向收缩,并随着成形压力的增大而减小;在较高的烧结温度下,成形压力和烧结时间对径向收缩几乎没有影响;而孔隙度、最大孔径和透气度随着成形压力的增大而降低,并随烧结时间延长而增大;增大成形压力,延长烧结时间,有利于提高Fe16Al2Cr多孔材料的剪切强度。     

连续梯度不锈钢多孔材料烧结变形分析

采用模压成形工艺制备连续梯度不锈钢多孔材料。试验对所制备的不同厚度连续梯度不锈钢多孔试样的收缩率及微观形貌进行了分析。结果表明：通过烧结试样的几何轮廓证实连续梯度多孔试样烧结后发生变形——相邻梯度层烧结应力的不同造成圆柱状试样烧结后变成圆台状;烧结过程中连续梯度多孔试样相邻梯度层间力的作用能够促进粉末烧结,对试样的烧结收缩产生影响,并且,粉末粒度越小,这种影响越明显;选择合适的级配粉末以及梯度层间合理的粉末体积或质量搭配,通过不同梯度层间烧结应力的相互抑制作用,可以实现同步收缩烧结,有效解决连续梯度不锈钢多孔材料烧结过程中出现的变形、开裂问题。     

反应合成法制备FeAl金属间化合物多孔材料的曲折因子(英文)

以Fe、Al元素粉末为原料,采用反应合成方法,利用Kirkendall效应造孔制备的FeAl金属间化合物多孔材料是继陶瓷和金属多孔材料之后发展的一种新型多孔材料。曲折因子是表征多孔材料孔隙特征的重要参数。基于Darcy原理和 Hagen-Poiseuille方程研究FeAl多孔材料的曲折因子。结果表明,FeAl多孔材料的曲折因子小于具有相同孔结构的不锈钢多孔材料的曲折因子。在本研究范围内,根据 Hagen-Poiseuille方程计算得知,FeAl多孔材料的曲折因子为2.26,而具有相同孔结构的不锈钢多孔材料的曲折因子为2.92。并由造孔机理探讨了FeAl多孔材料曲折因子较小的原因。     

粉末特性对多孔不锈钢制备工艺和结构的影响

以凝胶注模工艺为基础,结合微波烧结技术,制备了形状和孔隙可控的多孔不锈钢材料。采用扫描电子显微镜、密度仪、抗弯实验等手段研究了粉末粒径、粉末形状、固相含量等特性对多孔不锈钢制备工艺和孔隙形貌、孔隙率的影响。结果表明:粉末粒径越小,形状因子越大,胶体固相含量越高,制备得到的多孔不锈钢的孔隙率越高;粉末形状因子越小,多孔不锈钢的孔隙越不均匀;固相含量越高,虽然坯体强度有所提高,但凝胶体系的粘度也越大,流动性较差,适合不锈钢粉末凝胶注模的最佳固相含量在58%左右。通过控制颗粒直径、颗粒形状、固相含量及采用颗粒级配的方法,可实现对凝胶注模制备多孔不锈钢的孔隙结构和孔隙率的有效控制。     

Preparation and Pore Structure Stability at High Temperature of Porous Fe-Al Intermetallics

Porous Fe-Al intermetallics with different nominal compositions (from Fe-8 wt.% Al to Fe-50 wt.% Al) were fabricated by Fe and Al elemental powders through reaction synthesis. The effects of the Al content on the pore structure properties, and the comparison of pore structure stabilities at high-temperatures among the porous Fe-Al intermetallics and porous Ti, Ni, 316L stainless steel samples, were systematically studied. Results showed that the open porosity, maximum pore size, and permeability vary with the Al content. Porous Fe-(25-30 wt.%) Al intermetallics show good shape controllability and excellent pore structure stability at 1073 K in air, which suggests that these porous Fe-Al intermetallics could be used for filtration at high temperatures.     

不锈钢粉末与丝网复合的孔隙和透过性能

将不锈钢粉末与韧性丝网复合,通过变化材料、料浆粒度和覆层方式,可获得既具有金属的强韧、耐蚀和热震性,又可调结构及性能的柔性微孔材料,该微孔材料可冲压、折叠和焊接成复杂形状的滤芯.不锈钢粉末与丝网复合的孔隙和透过性能研究表明,料浆粒度显著影响孔隙和透过性能,末级料浆粒度起决定性作用;二次双向涂覆时,相同料浆粒度料浆形成外细内粗的三明治结构,不同粒度料浆形成由粗到细的梯度结构;复合多孔材料具有均匀的孔径分布和高透过率.     

Sintered Cu Alloyed Stainless Steels and Their Corrosion Behavior

Copper is an effective element to activate the sintering process of stainless steels and to enhance corrosion resistance of the sintered specimens. Ways of introducing Cu into stainless steel powders lead to different consequence in the microstructure and corrosion behavior of sintered Cu alloyed stainless steel. In the present work, two methods, mixing Cu with stainless steel powder and coating stainless steel powder with Cu by electroless plating, were introduced in order to investigate their influence on the sintered specimens. It was found that the sintered specimens from Cu-coated stainless steel powders (1-5 wt.%Cu) produce less porous surfaces with isolated pores than the specimens from mixed powders and the former have obviously high density and relatively even Cu distribution. Potentiodynamic polarization measurements indicate that Cu-electroless plating of 1-5 wt.%Cu improves the corrosion resistance of sintered stainless steel due to the lowering of passivation current density.     

球磨时间对TiC-不锈钢复合粉料粒度和组织的影响

以不锈钢粉末、钛粉和碳粉为原料，通过高能球磨法在真空条件下制备了不锈钢-TiC超细复合粉末。采用X-ray、扫描电镜、透射电镜、比表面积评价等分析技术对球磨过程中粉末的微观状态进行了分析。结果表明，随着球磨时间的增加，不锈钢复合粉末逐渐细化，最终可达到纳米级。同时，钛粉和碳粉在球磨过程中反应形成TiC．并在不锈钢晶内形成TiC纳米粒子。     

Structural and mechanical characteristics of porous 316L stainless steel fabricated by indirect selective laser sintering

Selective laser sintering (SLS) technique is capable of rapidly fabricating customized implants with porous structure. A simple encapsulation process was developed to coat 316L stainless steel (316L SS) powder with ethylene-vinyl acetate copolymer (EVA). Subsequently, porous 316L SS was prepared by SLS preforming of EVA-coated metal powders, debinding and sintering in hydrogen atmosphere. The effects of processing parameters on pore characteristics and mechanical properties were analyzed. The results indicate that the porosity of green body mainly depends on laser energy density, while the pore features and mechanical properties of sintered specimens are largely dominated by sintering temperature. After sintering at 1100–1300 °C, the average pore size and porosity are 160–35 μm and 58–28%, respectively. In addition, the elastic modulus and compressive yield strength are 1.58–6.64 GPa and 15.5–52.8 MPa, respectively. It is revealed that the pore structural parameters and mechanical properties of the as-sintered porous 316L SS can be controlled readily to match with those of cancellous bone by modification of SLS processing parameters and subsequent sintering temperature.     

多孔结构分形分析及其在材料性能预报中的应用

采用分形理论表征孔隙的结构特征,通过对烧结不锈钢纤维多孔材料的扫描电镜(SEM)照片进行图像处理和分形分析,详细研究图像分辨率、获取图像时的放大倍数、灰度图转化为二值图时阈值的大小等因素对孔结构分形分析结果的影响,并研究它们与分形维数的定性关系.结果表明,采用的烧结纤维多孔材料具有明显的分形特征,图像分辨率、放大倍数、阈值等因素对分形维数计算结果影响显著:与SEM图像的原始分辨率相比,分辨率变化越大则分形维数越大;分形维数随着放大倍数的增大而减小;灰度图转化为二值图时的阈值存在最佳值,且随着阈值的增大,分形维数先增大后减小.通过理论推导,建立了多孔材料孔隙度和渗透性能与孔结构分形维数之间的数学关系.可通过孔结构分形维数、面孔隙度、孔径等参数合理预测多孔材料的体孔隙度、渗透性能,预测结果与实测结果吻合良好.     

Phase formation in cemented carbides prepared from WC and stainless steel powder – An experimental study combined with thermodynamic calculations

Cemented carbides prepared from mixes of WC and stainless steel powder have been proposed as possible alternatives to WC-Co. However, phase formation in such systems is not well described in the literature, in particular with regard to the possible formation of Cr-carbides. In this work, cemented carbides have been prepared from batches of coarse WC powder and 20 wt% AISI 360 L stainless steel powder, considering different carbon black additions to vary the final carbon contents to 4.9, 5.64, 5.75 wt% C. Both experimental results and thermodynamic calculations show that no classical two phase area – containing only WC and metallic binder- can be expected in these alloys. (Cr, Fe)-carbides are observed at all carbon contents in equilibrium with eta phases and binder, and at the highest carbon content also with graphite. As a consequence of the formation of (Cr, Fe)-carbides the amount of metallic binder decreases significantly, and the composition of the binder changes drastically. The binder phase in the sintered materials constitute an Fe-15Ni alloy with about 5 wt% Cr and 2 wt% W in solid solution, which is more similar to a maraging steel rather than a stainless steel. Both thermodynamic calculations and experimental results confirm that the maximum amount of Cr that can be retained in the metallic binder is around 5 wt% Cr which implies that, after sintering, the stainless steel properties will be lost.