表面活性剂对金属粉末注射成形喂料性能的影响

研究了表面活性剂对聚乙二醇-聚甲基丙烯酸甲酯/Fe-2Ni粉末注射成形喂料性能的影响。首先用单分子层吸附模型计算出形成单分子层吸附所需表面活性剂的理论值,然后分别将硬脂酸、司班-20、司班-80、吐温-60等不同表面活性剂加入粘结剂中,发现表面活性剂可通过降低粘结剂对粉末的润湿角、降低粘结剂-粉末喂料的粘度而提高最大粉末装载量,在超过单分子层吸附的量之后,继续增加表面活性剂、仍能进一步发挥其有益作用。不同表面活性剂对喂料性能影响的程度有所不同,通过选择合适的表面活性剂,该聚乙二醇-聚甲基丙烯酸甲酯粘结剂对Fe-2Ni羰基粉末装载量达55%（体积分数）。     

陶瓷注射成型热脱脂与水基脱脂的机理研究

分别对Y-TZP陶瓷粉的石蜡基热脱脂体系和水溶性的聚乙二醇（PEG）基水脱脂体系的脱脂过程和机理进行了研究。研究表明，由石蜡基注射料在空气中的热失重曲线制定的脱脂制度，脱脂过程耗时47h；而通过宽分子量的PEG得到水基粘结剂体系，注射成型后的坯体在40℃的水中浸泡2h，可以除去65％的PEG，坯体外观良好。通过SEM证明了此时形成了由外到内的孔道；然后可以不用埋粉进行快速热脱脂，6h可基本脱除剩余粘结剂。最后，2种脱脂体系均得到了强度高于800MPa的烧结样条。     

Ni基包裹型超细WC复合粉体制备的实验研究

采用一步碳化法将制得的超细WO3粉体还原为超细WC粉体,通过非均相沉淀法,将超细WC粉均匀悬浮在溶液中,让镍盐在WC粉体上生成沉淀并生长,形成包裹层,通过高温分解、还原,生成均匀Ni基包裹型超细WC的复合粉体,同时分析了预处理(分散)、滴加方式、反应液浓度对包裹效果的影响.结果表明,聚乙二醇PEG2000作为分散剂制得的包裹粉分散效果最好;分散的WC分批加入到反应液中减少了WC胶粒聚沉,改善了包裹粉的分散效果;包裹反应时逐滴慢速加入滴加方式可以得到包裹效果好的包裹粉;Ni包裹超细型WC粉体的物相为面心立方Ni和WC,符合热喷涂实验所要求的超细结构喂料.     

粉末注射成形热塑-热固粘结剂的开发研制

介绍了硬质合金粉末注射成形用热塑 -热固性粘结剂RG1- 2、RG2 - 3的开发研制过程。结果表明 :在注射完成之前 ,粘结剂和喂料完全表现为热塑性 ,该粘结剂可直接应用于热塑性注射机。喂料的低温流变性能好 ,粉末临界装载量达到 5 9%。RG1- 2、RG2 - 3注射生坯强度分别达到 5 .8MPa和 7.8MPa ,固化后成形坯强度分别达到 17.6MPa和 19.1MPa。采用该粘结剂及相应的注射成形工艺制备的YG8、YT5硬质合金强度分别达到 2 480MPa和 2 10 0MPa ,硬度分别达到HRA89.7和HRA90 .4,制品最小尺寸偏差达到± 0 .0 2mm ,尺寸精度及保形性优于传统蜡基粘结剂。     

新型改性磷酸盐无机粘结剂热硬砂性能研究

合成了一种新型磷酸盐无机粘结剂,探究了其硬化工艺,并测试了粘结剂热硬砂常温抗压强度、抗吸湿性、溃散性等性能。结果表明,该粘结剂砂的抗压强度高、抗吸湿性好、溃散性好,是一种性能优异的新型铸造用无机粘结剂。     

CO2固化纳米SiO2/甲阶碱性酚醛树脂的研究

考察用聚乙二醇修饰的纳米SiO2在树脂溶液中分散性;利用透射电镜、红外光谱研究了聚乙二醇(PEG)修饰的纳米SiO2表面性能及分散性的改进效果;并通过砂芯抗压强度来研究纳米SiO2的用量对CO2固化酚醛树脂粘结剂抗压强度的影响,结果表明:4%聚乙二醇修饰的纳米SiO2粒子在树脂溶液中分散性较好;纳米SiO2粒子表面羟基减少;添加量在0.3%时,粘结剂的抗压强度可以提高30%.     

铸造3D打印用双组分自硬磷酸基粘结剂的研究

合成了一种铸造3D打印用双组分自硬磷酸基粘结剂,探究了其常温强度、抗吸湿性、溃散性、固化速度、稳定性等使用性能。结果表明,该双组分自硬磷酸基粘结剂的常温强度高、粘度低、溃散性好、抗吸湿性能优异、硬化速度快、体系稳定,是一种性能优异的铸造3D打印用粘结剂。     

316L不锈钢粗粉注射成形喂料的流变行为

制备了平均粒度为30μm的316L不锈钢粗粉注射成形喂料,研究了剪切速率、温度对喂料流变行为的影响,应用毛细管粘度计测量了3种喂料在不同温度下的粘度值,比较了3种不同成分喂料的应变敏感性因子的大小。结果表明:粉末装载量为58%、粘结剂成分为65%PW+30%LDPE+5%SA的喂料应变敏感性因子较小,较适合316L不锈钢粗粉的注射成形。     

注射成型用氧化锆粉体的表面改性研究

陶瓷粉体在高分子粘结剂中的分散性以及注射喂料的流动性是陶瓷粉末注射成型的关键因素.由于高分子的分子结构和物理形态与陶瓷粉体不同,导致两者相容性差.并且陶瓷粉体表面自由能较高,与高分子粘结剂混合过程中会有团聚的倾向.本研究采用硬脂酸对氧化锆粉进行表面改性,降低了粉体的表面自由能,提高了喂料的均匀性.改性后的陶瓷粉体表面由亲水性变为亲油性,提高了粉体与粘结剂的相容性,降低了喂料体系的粘度.     

应用于陶瓷注射成型技术的SIPM-PEG 基水溶性粘结剂

研究了水溶性聚酯SIPM-PEG作为水溶性粘结剂在陶瓷注射成型技术中的应用.通过分子量分别为200和400的聚乙二醇(PEG)与间苯二甲酸二甲酯-5-磺酸钠(SIPM)的缩聚反应制备了2种水溶性聚酯,并且将乙烯醋酸乙烯共聚物(EVA)和聚乙烯醇缩丁醛(PVB)作为骨架粘结剂,制备了Al2O3注射料.研究了粘结剂的组成和各组分的含量对Al2O3注射料的水脱脂速率、流变性和生坯强度的影响.     

Novel PEG-based binder system and its debinding properties for MIM

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A new starch-based binder for metal injection molding

A composition of starch and linear low-density polyethylene (LLDPE) was prepared as the binder and a mixture of this binder with 316L stainless steel powder was used to achieve a feedstock with 57% vol. powder loading. Rheological specifications of the binder and the feedstock were observed by means of capillary rheometery. Pseudo-plastic behavior of the binder and feedstock was investigated as a necessity in metal injection molding (MIM) process by proper flow characterization tests and their viscosity as the most significant flow characteristic was obtained in acceptable ranges. Thermogravimetric analysis (TGA) was carried out on feedstock in order to understand decomposition behavior of the binder components. In the next step, injection molding of the components was successfully conducted. Mechanical properties of compacts were then investigated through the triple point flexure test and the results showed that mechanical strength of specimens are very close to established ranges. The density of green parts was measured to assess the compaction of feedstock and it was achieved within the expected range for ferrous-based feedstocks. Debinding process was accomplished on compacted articles at three different temperature ranges including 70, 80 and 90 °C. Sintering process also was successfully accomplished on samples. For observing microstructures, the surface and cross section of specimens were compared before and after debinding as well as after sintering using scanning electron macrograph (SEM). Generally, this newly developed binder demonstrated a good potential for being utilized in MIM process.     

RHEOLOGICAL PROPERTIES OF METAL INVECTION MOLDING BINDER AND FEEDSTOCK

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Rheological properties of metal injection molding feedstock

Viscosity of a polyethylene glycol-polymethyl methacrylate (PEG-PMMA) binder and PEG-PMMA/Fe-2Ni feedstock in powder injection molding was measured and calculated. A logarithmic additivity between viscosity of the binder and that of its constituents was found. Other factors, such as temperature, powder loads, content and type of surface-active agents and those of polymers, in relation to rheological properties of feedstock were discussed as well. The results showed that with increasing viscosity of surface-active agent, polymer melt index or temperature, the feedstock viscosity decreased while higher polymer content and powder loading would lead to additional feedstock viscosity. The relationship mentioned above is expressed and effectively explained why the change rate of feedstock viscosity will slow down with the increase of shear rate.     

Fabrication of 93W–Ni–Fe alloy large-diameter rods by powder extrusion molding

A powder extrusion molding (PEM) process has been used for the manufacturing of tungsten heavy alloy rods with large length to diameter ratio. An improved wax-based multi-component binder was developed for PEM of 93W–Ni–Fe alloy. The miscibility of its components and the characteristics of the binder were evaluated and good thermal–physical properties were obtained. Also, the feedstock rheological properties, extrusion molding and debinding process were studied. The feedstock exhibited a pseudo-plastic flow behavior. The large length to diameter ratio rods, with diameters up to 36 mm were extruded at 65 °C by optimizing the extrusion process. A two-step debinding process was employed to remove the binder in the extruded rods. Solvent debinding was carried out in n-heptane at 45 °C to extract the soluble components. A process of repeated short time immersion and drying of the extruded rods (called short-period solvent debinding) was developed and using this novel technique the binder removed was raised from 45% to 60%. SEM analyses indicated that a large volume of pores was formed in debound rods, but had not created interpenetrating pore channels yet. The rest of the binder could be thermally extracted at a high heating rate without defects.     

钨基合金增塑粉末挤压成形新技术

采用增塑粉末挤压成形新技术,开发了几种适合钨基合金挤压成形用粘结剂,研究几种配方粘结剂的相容性及挤压、脱脂特性。通过热力学计算和热分析,以及扫描电镜和偏光显微镜观察,发现粘结剂各组元分子间具有较好的相容性。通过优化喂料制备、挤压工艺,分别在60和75℃制备出直径达24mm的大长径比钨基合金棒材。综合采用溶剂-热两步脱脂工艺,实现Ф24mm挤压棒坯的快速无缺陷脱脂。     

硬质合金挤压成形喂料热脱脂特性

开发出了适用于硬质合金挤压成形的成形剂及相应的热脱脂技术，通过优化配方设计与制备方式及工艺条件，制得了性能优良，分布均匀的成表剂。研究了成形剂及喂料的热脱脂工艺与机遇，发现热脱脂可分为低温区与高温区2个阶段，其脱脂机理均为热扩散，但2阶段热脱脂反应活化能不同；无论是成形剂还是喂料，其它组元的加入起了催化剂的作用，能有产地降低热脱脂反应活化能。     

硬质合金增塑粉末螺杆挤压成形

探讨了用于硬质合金粉末螺杆挤压成形技术的新粘结剂制备及挤压棒的组织形貌。新粘结剂由几种低分子量组元与1种热塑性弹性体高分子组元构成。采用溶剂溶解与加热熔融相结合的办法制备粘结剂。室温下，用合适的剪切力搅拌，能很快将粘结剂与YG8粉末混合均匀，制得组成均一的料浆式挤压用喂料。用扫描电子显微镜观察了挤压毛坯的微观组织及脱脂试样的组织结构与缺陷。用热重(TG)与微分热重(DTG)方法研究了热脱脂机理与动力学，发现了三维扩散控制热脱脂的速率。在脱脂的第1阶段，低分子量组元被脱除掉，挤压毛坯内形成了连通毛细孔。在脱脂的第2阶段，剩下的高分子量组元被完全脱除；第2阶段的热脱脂能以较快的升温速率进行。制备出了φ20mm的硬质合金挤压棒。     

Thermo-physical characterization of binder and feedstock for single and multiphase flow of PIM 316L feedstock

A thorough knowledge of the material properties of the feedstock and binder system is essential for successful powder injection moulding (PIM) as well as for numerical simulation. In view of the above, characterization of a developed binder system and feedstock has been reported in this paper for processing of 316L stainless steel powder through PIM route. The binder system consists of paraffin wax, stearic acid and low-density polyethylene. The feedstock comprises of 316L stainless steel powder and the above binder system. The thermal, physical and rheological characteristics of the binder system and feedstock have been investigated separately along with binder removal technique from the injection-moulded green compact. The thermal characterization revealed the semi-crystalline nature having distinct melting and solidification range for both the binder and feedstock. Data from DSC and TGA show that injection of the feedstock should be carried out above 102 °C (i.e. the upper melting temperature) but below 154 °C as beyond which the binder components paraffin wax and stearic acid start degrading and mould temperature should be below 57 °C. The binder and feedstock are found as shear-thinning fluid as viscosity decreases with the increase in shear strain rate and temperature. However, the viscosity of the binder is more sensitive to shear strain rate and temperature compared to that of the feedstock.