微晶蜡对MIM多元蜡基粘结剂性能的影响

研究了微晶蜡MW的加入对PW-EVA-HDPE蜡基粘结剂、喂料的均匀性、流变特性的影响。对比实验发现MW加入不会明显改变粘结剂的粘度，加入20％MW(质量分数)的蜡基体强度提高了5倍，体积收缩率降低到6．44％，使多元蜡基粘结剂从粗大层片状(50μm-150μm)结晶细化为均匀的微细晶(5μm～8μm)；一定量的MW可以改善PW-EVA-HDPE三元蜡基粘结剂的组织均匀性和热稳定性，升高注射温度，能提高粉末装载量和粉末在粘结剂中分散的均匀性，从而提高产品的成品率和尺寸精度。     

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.     

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

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

工艺参数对金属注射成形坯缺陷的影响

采用ＭＩＭ标准拉伸试样模具,研究注射过程主要工艺参数即注射温度,注射压力,模具温度对注射过程缺陷的影响,获得了最佳注射工艺参数,对欠注,断裂,中心通孔等几种缺陷的形成机制作了分析,并提出了ＭＩＭ成形范围图的概念。     

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

1　ＩＮＴＲＯＤＵＣＴＩＯＮＭｅｔａｌｐｏｗｄｅｒｉｎｊｅｃｔｉｏｎｍｏｌｄｉｎｇ (ＭＩＭ )ｉｓａｎｅ ｍｅｒｇｉｎｇａｄｖａｎｃｅｄｎｅｔ ｓｈａｐｉｎｇｔｅｃｈｎｏｌｏｇｙ ,ｗｈｉｃｈｏｆ ｆｅｒｓｉｍｐｏｒｔａｎｔａｄｖａｎｔａｇｅｓｏｖｅｒｔｈｅｃｏｎｖｅｎｔｉｏｎａｌｐｏｗ ｄｅｒｍｅｔａｌｌｕｒｇｙ .Ｔｈｉｓｔｅｃｈｎｏｌｏｇｙｈａｓａｔｔｒａｃｔｅｄｍｏｒｅａｎｄｍｏｒｅａｔｔｅｎｔｉｏｎａｎｄｕｎｄｅｒｇｏｎｅｒａｐｉｄｄｅｖｅｌｏｐｍｅｎｔｉｎｔｈｅｒｅｃｅｎｔｙｅａｒｓ[1～ 4 ] .…     

热等静压及后续热处理对MIM418涡轮合金组织与性能的影响

比较了热等静压前后MIM418合金组织与致密度的变化,研究了不同淬火(水冷和空冷)、时效工艺对热等静压后固溶态MIM418合金微观组织及各种析出相的影响,利用扫描电镜、透射电镜、能谱分析等手段分析了合金中主要强化相γ'和碳化物二者的形态、大小和分布的规律。结果表明,热等静压可明显提高MIM418合金的致密度,但对显微组织影响不大,"固溶+中温时效"可以获得较好的硬化效果,主要析出强化相γ'和二次碳化物的析出受固溶冷却方式的影响较大,γ'相纳米化和二次碳化物的析出或将有益于MIM418硬度的大幅度提高。     

Pore opening and binder flow during initial stage of thermal debinding in MIM

1　INTRODUCTIONMetalinjectionmolding(MIM )isanet shapingtechnology ,whichhasthecharacteristicsoftheplas ticinjectionmoldingandconventionalpowdermetal lurgy(PM ) .MIMenablestheproductionofproductswithgreatershapecomplexity ,andwithbetterper formances.This processconsistsofthefollowingsteps :certainamountofbinderisblendedwithprop erpowders ,inorderforpreparingsuitablefeed stockstoinjection ;afterinjectionmolding ,partsarede boundandthensinteredandinthiswayfinalproductsareformed[1,2 ] .Th…     

Deformation behavior and strength evolution of MIM compacts during thermal debinding

Effects of the debinding atmosphere, powder characteristic, solid loading and heating rate on the compact deformation were investigated. The compact strength after thermal debinding was measured by bending mode. The experimental results indicate that the vacuum atmosphere is beneficial to improving the deformation resistance compared with nitrogen atmosphere. Small particle size, irregular particle shape and high solid loading are suitable for decreasing the deformation defects. Besides, too fast heating rate may induce deformation defects. It is also indicated that effect of the factors for the deformation defects is different in different debinding stages. The strength evolution of the compacts during thermal debinding was also discussed.     

注射成形铜/钨复合材料溶剂脱脂行为研究

以注射成形铜/钨复合材料生坯为研究对象,采用二氯甲烷为溶剂,对成分为CuW5以及CuW15的两种成分的生坯,采用不同粉末装载量、不同形状的试样进行溶剂脱脂。重点考察了溶剂脱脂工艺参数对脱脂行为的影响,还就坯件本征特点对于溶剂脱脂行为的影响进行了分析探讨,最后计算了本实验条件下,用二氯甲烷脱脂的动力学参数,为后续实验条件的设定提供了理论依据。实验结果显示,脱脂温度与时间对于溶剂脱脂是综合外因;在研究脱脂行为时,考虑坯件本体特征的影响十分重要,坯件厚度对于溶剂脱脂影响很大,形状的复杂性几乎不影响脱脂率。粉末形态不够规则,生坯内部孔隙多,溶剂脱脂更易持续进行,达到更大的脱脂量。脱脂初期脱脂速率由扩散控制,呈线性变化,当脱脂时间达到10h以后,脱脂速率将转变为由溶解和扩散混合控制。     

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

1　INTRODUCTIONPowderinjectionmolding (PIM ) ,whichisde rivedfromplasticinjectionmolding ,isakindofnet shapepowdermetallurgyformingprocess[13] .Com bininghigh partcomplexitywithhigh productionquantities ,itsupplementstheestablishedprocesseslikediecompaction ,machiningandinvestmentcasting[4 6 ] .Comparingtoconventionalpressing/sinteringprocess,thePIMhasgreattechniqueandcostadvantagesforthepro ductionofcementedcarbidecomponentswithcomplexshapes[7,8] .Sincehydraulicpressureisappliedduringi…     

硬质合金刺刀座注射成形工艺过程的研究

研究了硬质合金刺刀座注射成形工艺过程。结果表明 :金属注射成形可以生产出性能优良、形状复杂的硬质合金刺刀座 ;MIM工艺生产硬质合金制品与传统的 P/ M法相比 ,制品的尺寸精度较难控制。     

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）。     

Fabrication of metal matrix composites by metal injection molding—A review

Metal injection molding (MIM) is a near net-shape manufacturing technology that is capable of mass production of complex parts cost-effectively. The unique features of the process make it an attractive route for the fabrication of metal matrix composite materials. In this paper, the status of the research and development in fabricating metal matrix composites by MIM is reviewed, with a major focus on material systems, fabrication methods, resulting material properties and microstructures. Also, limitations and needs of the technique in composite fabrication are presented in the literature. The full potential of MIM process for fabricating metal matrix composites is yet to be explored.     

Rheological, mechanical and corrosive properties of injection molded 17-4PH stainless steel

The feedstock based on the binder 65％PW-30％ EVA-5％SA has the best general rheological properties for the 17-4PH stainless steel powder. The 17-4PH stainless steel compacts sintered at 1380℃ for 90 min have the best mechanical properties and the good microstructure with homogeneously distributed pore structure and the moderate-sized grains. Whereas the compacts sintered for 60 min and 120 min show an inadequate and an over-sintered microstructure respectively. The compacts sintered at 1380℃ for 90 min have the density of 7.70 g/cm^3 , the strength of 1 275 MPa, the elongation of 5％, and hardness of HRC36. With the increase of sintering temperature, the density, strength and hardness increase, while the elongation decreases. The 17-4PH stainless steel has good corrosion resistance, showing an activation-passivation polarization curve. But the passivation potential range is narrow and the spot corrosion potential is low, indicating a low anti-spot corrosive properties.     

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。     

金属注射成型(MIM)综合脱脂炉的结构设计特点

介绍了金属注射成型(MIM)综合脱脂炉的结构设计特点,该设计可同时满足包括溶剂、催化、冷凝蒸汽、虹吸脱脂在内的脱脂工艺要求.     

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。     

金属粉末注射成形过程计算机模拟技术的现状及发展

简要阐述了金属粉末注射成形计算机模拟技术的基本原理、发展历史、研究现状及其发展前景,并提出了开发本国金属粉末注射成形计算机模拟技术软件的必要性和迫切性。     

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。     

粉末注射成形粘结剂组分相容性的热力学判据

对粉末注射成形粘结剂组分的在数进行了计算，并通过实验观察得到了组分相容性的判据。分别以PVB，EVA，PMMA为高分子组分，讨论了它们与低分子量组分PEG的相容性，并通过混炼机混炼和偏光显微镜观察，得到了△G/T〈1、5可供工艺相容、 △G／T＞3．0不相容的热力学判据。