金属注射成形用新型聚乙二醇基粘结剂的研究

研究了一种新型聚乙二醇（PEG）基热塑性粘结剂,它由高密度聚乙烯、聚乙二醇、聚合物W、硬脂酯、邻苯二甲酸和二辛脂和抗氧剂等组成。新型PEG基粘结剂与Fe-2Ni粉具有较强的相互作用,混合均匀性好,且粉末装载量高,喂料注射成形性好。用新型PEG基粘结剂和Fe-2Ni粉所制备的喂料是一种假塑性流体,具有良好的流变性能。新型PEG基粘结剂用乙醇溶剂脱脂,速度快、缺陷少、维形能力强,且可避免环境污染。     

聚乙二醇基粘结剂用于Fe—2Ni注射成形的研究

研究了用于Ｆｅ－２Ｎｉ（质量分数,％,下同）注射成形的聚乙二醇－聚甲基丙烯酸甲酯粘结剂的制备。粘结剂混炼时间短,粉末装载量５５（体积分数,％）,Ｈ２Ｏ脱脂速度超过２ｍｍ／ｈ。     

注射成形无镍奥氏体不锈钢喂料的流变性能研究

以气雾化法制备的Cr17Mn11Mo3N无镍奥氏体不锈钢粉末和蜡基粘结剂为原料,混合制备了不同的喂料。利用RH5000型高压毛细管流变仪,研究了粘结剂配比和粉末装载量对喂料流变性能的影响。采用Second Order模型回归分析,计算出了非牛顿指数n、粘流活化能E和综合流变学因子α_(STV)。结果表明,所制备的喂料均呈假塑性流体特性。该粘结剂体系配比为65%微晶蜡(MW)、25%高密度聚乙烯(HDPE)、5%乙烯-醋酸乙烯共聚物(EVA)和5%硬脂酸(SA),粉末装载量为68 vol%,喂料具有较好的综合流变性。     

粘结剂配比对316L不锈钢粉末注射成形喂料流变行为的影响

制备了58%粉末装载量、不同粘结剂配比的316L不锈钢粉末注射成形喂料,对比了各粘度模型的应用范围。采用Second Order模型回归了喂料的各项流变参数,分析了剪切速率和温度对喂料粘度的影响。结果表明,Second Order模型适合用于描述实验喂料的流变行为,剪切速率和温度对喂料粘度的影响规律:粘度随剪切速率和温度的升高而降低。该粘结剂体系的最佳配比为65%石蜡、30%低密度聚乙烯及5%硬脂酸,考虑了剪切速率和温度对粘度的影响,其流变行为公式为lnγ=2.1335-0.9717lnγ+0.107T-0.0511(lnγ)2+0.0066T lnγ-0.0005T2。     

粉末粒形对钨粉末注射成形喂料流变性能的影响

本文采用图像法定量表征了钨粉的粒形与粒度,研究了粉末粒形对钨粉末注射成形喂料流变性能的影响。结果表明：窄粒径钨粉（NPW）与球形钨粉（SW）粒度基本一致;SW比NPW具有更好的球形度、表面光滑度以及分散度。采用相同的有机粘结剂,SW的粉末装载量为64%,高于NPW的59%。与NPW相比,SW喂料表现出更优异的流动性能,具有更低的流动行为指数和粘流激活能,更适合注射成形。粉末粒形影响钨MIM喂料的流变性能主要源于粘结剂与粉末颗粒以及颗粒与颗粒之间的相互作用特性。     

表面处理对磁粉抗氧化性及注射成形粘结磁体的影响

对NdFeB磁粉进行了不同表面处理,研究了表面处理对磁粉抗氧化性、喂料流动性及粘结磁体性能的影响规律.结果表明:(1)NdFeB磁粉经改性处理后,粉末在300℃及500℃的氧化增重率大大降低;而且采用先磷酸后硅烷的复合处理工艺要比单一的硅烷处理或单一的磷酸处理效果更好;(2)KH550硅烷耦联剂能有效地改善NdFeB磁粉与尼龙粘结剂相容性,相应制得的喂料流动性要好于未改性磁粉,而且能相对提高NdFeB磁粉的装载量,使得最大装载量(体积分数)达到67%;(3)通过对磁粉表面改性,改善了磁粉与塑料粘结剂的界面特性,不仅提高了注射成形粘结磁体的磁学及力学性能,而且改善了粘结磁体的耐热性能.     

注射成形钛合金粉末流变特性

以Ti?6Al?4V合金粉末为原料,选用60%(质量分数)石蜡、35%低密度聚乙烯和5%硬脂酸为粘结剂配方制备注射成型喂料。采用毛细管流变仪测定喂料的流变参数,分析不同球磨时间、粉末装载量、温度下喂料的流变学性能。结果表明：随着球磨时间的增加,喂料粘度增加,n 值减小;粉末装载量越高,喂料的粘度值越大,而且粘度与粉末装载量满足经验公式： mA ?=?=(1/)/ maxbr φφηηη,经计算,m的值为0.33。粘性流动激活能Ea值随剪切速率的增加而减小。     

金属注射成形17-4PH不锈钢脱脂保形性研究

研究了粘结剂配方，粉末装载量，喂料热力学性质，注射成形工艺等多个因素对金属注射成形17-PH不锈钢脱脂保形性的影响。结果表明具有较高热分解温度，较低熔解热的HDPE作为第2组元的蜡基粘结剂，具有比采用EVA为第2组元的粘结剂更好的保形性能。试样变形率随着粉末装载量，注射压力，注射温度的增加而下降，而且存在一最佳的工艺条件，包括粉末装载量，注射压力，注射温度，此时试样最不容易变形，试样变形比例最小。     

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。     

Ti-6Al-4V合金喂料临界粉末装载量的研究

研究了4种不同蜡基粘结剂配方下钛合金喂料的临界固体粉末含量,并测试了临界固体粉末含量下喂料的流变学参数。实验结果表明:1#喂料(100%PW)、2#喂料(95%PW+5%SA)、3#喂料(70%PW+25%PE+5%SA)、4#喂料(60%PW+35%PE+5%SA)的临界粉末装载量(vol.%)分别为:70%,71.53%,72.24%,73.02%;经流变学分析,临界粉末装载量下喂料仍呈假塑性流体,但其流动指数n值较小,在0.2以下,不利于成形。     

Effects of milling and active surfactants on rheological behavior of powder injection molding feedstock

ＩＮＴＲＯＤＵＣＴＩＯＮＰｏｗｄｅｒｉｎｊｅｃｔｉｏｎｍｏｌｄｉｎｇ (ＰＩＭ )ｆｉｔｓｅｓｐｅｃｉａｌｌｙｆｏｒｍａｎｕｆａｃｔｕｒｉｎｇｃｏｍｐｌｅｘｓｈａｐｅｄｐａｒｔｓｏｆｃｅｒｔａｉｎａｌ ｌｏｙｓｗｉｔｈｈｉｇｈｐｅｒｆｏｒｍａｎｃｅ[1 ] .Ｈｏｗｅｖｅｒ,ｄｕｅｔｏｔｈｅａｇｇｌｏｍｅｒａｔｅｄｉｒｒｅｇｕｌａｒｓｈａｐｅ,ｆｉｎｅｐａｒｔｉｃｌｅｓｉｚｅ,ｈｉｇｈｉｎｎｅｒｐｏｒｅｓａｎｄｓｐｅｃｉｆｉｃｓｕｒｆａｃｅａｒｅａｏｆｔｈｅｉｎｉｔｉａｌｔｕｎｇｓｔｅｎｐｏｗｄｅｒ,ｔｈｅ…     

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.     

IMPROVEMENT OF RHEOLOGICAL AND SHAPE RETENTION PROPERTIES OF WAX-BASED MIM BINDER BY MULTI-POLYMER COMPONENTS

ＩＮＴＲＯＤＵＣＴＩＯＮＭｅｔａｌｉｎｊｅｃｔｉｏｎｍｏｌｄｉｎｇ（ＭＩＭ）ｉｓａｎｅｍｅｒｇｉｎｇｎｅｔｓｈａｐｉｎｇｐｒｏｃｅｓｗｉｔｈｔｈｅｃａｐａｂｉｌｉｔｙｏｆｐｒｏｄｕｃｉｎｇｃｏｍｐｌｅｘｍｅｔａｌｐｒｏｄｕｃｔｓｗｈｉｃｈｃａｎ?..     

Effects of surfactant on properties of MIM feedstock

Effects of the surfactant for improving the properties of MIM feedstock were investigated. Feedstocks were prepared by 17-4PH stainless steel(SS) powder and paraffin wax-based binder containing different contents of stearic acid(SA) as the surfactant. The viscosity of the feedstock decreases significantly when the SA is added. Besides, the wetting angle of the binder against the 17-4PH SS powder decreases greatly and the critical solid loading increases with the adding of the SA. Fourier transformation infrared spectroscopy(FTIR) analysis was used to prove the interaction between the SA and the 17-4PH SS powder. Chemical bonding is found on the surface of 17-4PH SS powder after mixing and it helps a lot to enhance the interacting force between the binder and the powder. Then an adsorbing model was adopted to estimate the least content of the surfactant that formed a monolayer adsorption on the mono-sized spherical powder (with smooth surface). The least content of the surfactant is calculated to be 0.19%. Whereas, the experiments indicate that about 5% is the optimal value to improve the properties of the feedstock. The reason may come from two aspects: firstly, the powders used in current experiment are not all mono-sized spheres and the coarse surface of the powder has a great effect on the adsorptive capacity of the powder; secondly, multilayer adsorption is likely to occur on the powder surface, which will also increase the adsorptive capacity.     

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.     

Relationship between binder contents and mechanical properties of 17-4 ph stainless steel fabricated by PIM process and sintering

Mechanical properties and microstructures of 17-4 ph stainless steel parts produced using different binder contents (powder loading) of powder injection molding (PIM) feedstock have been studied. The tensile and wear properties have been evaluated. Wear tests were conducted by a pin-on-disk tribometer, without lubricant, at different loads and sliding distance. SEM examination of the fracture sufaces revealed good particle bonding and a high ductile fracture surface for high powder loading. The surface fractures of the bars with higher powder loading show a closed porosity. High performance properties such as fully dense, ultimate tensile strength, hardness and wear resistance are obtained with high powder loading.     

两种形状Nd-Fe-B粉末的混炼

采用快淬法和雾化法制得的2种不同形貌的NdFeB磁粉，以尼龙12作粘结剂，研究了注射成形粘结磁体的混炼过程。结果表明：混合料的均匀度与混合时间的关系近似符合Boltzmann方程，磁通热损失率近似符合指数函数，混合料的流变符合假塑性流体的特征；平均粒度相当的粉末、雾化粉的临界充填率、初始均匀度和充分混合后的均匀度都高于快淬粉；相同剪切速率下，雾化粉的粘度远比快淬粉低。     

RHEOLOGICAL PROPERTIES OF METAL INVECTION MOLDING BINDER AND FEEDSTOCK

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工程陶瓷注射成型的研究与发展

综述了陶瓷注射成型目前的发展状况以及该成型方法的优点。详细论述了陶瓷粉体性质、有机载体组成特别是表面活性剂对于陶瓷喂料和注射成型所成坯体性质的影响。分析了混炼顺序、注射工艺参数、脱脂对陶瓷喂料的流变性以及所成型坯体性质的影响。