Fe-2Ni粉末注射成形溶剂脱脂相关问题的研究

本文对石蜡-油-聚烯烃粘结剂溶剂脱脂相关问题进行了研究,包括溶剂和聚合物种类对脱脂过程的影响,脱脂坯强度、脱脂后干燥、溶剂回收等.结果表明:用二氯甲烷作溶剂脱脂速率高于三氯甲烷;温度升高溶剂脱脂速率增加,脱脂速率可达到2mm/hr;乙烯-醋酸乙烯共聚物(EVA)作聚合物组份,溶剂脱脂后开裂,这与EVA在溶剂中的溶胀率较大有关,坯块强度随脱脂进行而降低;石蜡-油在溶剂中累积使脱速率有所降低,可通过蒸溜方法使溶剂回收,回收率95%(质量分数)以上.     

Fe-2Ni粉末注射成形溶剂脱脂相关问题的研究

对石蜡-油-聚烯烃粘结剂溶剂脱脂相关问题进行了研究,包括溶剂和聚合物种类对脱脂过程的影响,脱脂坯强度、脱脂后干燥、溶剂回收等．结果表明：用二氯甲烷作溶剂脱脂速率高于三氯甲烷;温度升高溶剂脱脂速率增加,脱脂速率可达到2 mm/h;乙烯-醋酸乙烯共聚物(EVA)作聚合物组份,溶剂脱脂后开裂,这与EVA在溶剂中的溶胀率较大有关,坯块强度随脱脂进行而降低;石蜡-油在溶剂中累积使脱速率有所降低,可通过蒸溜方法使溶剂回收,回收率质量分数达95％以上．     

金属粉末注射成形石蜡-油-聚乙烯粘结剂的研究

本文开发了用于Fe-2Ni粉末注射成形石蜡-油-聚乙烯粘结剂,选择了石蜡和聚乙烯组份,考察了油的加入对组份相容性、生坯强度、粉末装载量、喂料热容、溶剂脱脂速率的影响.该粘结剂用于Fe-2Ni注射成形,粉末装载量达60%(体积分数),生坯强度5.5MPa,溶剂脱脂速率2mm/h以上.     

Ti-Mo吸气材料注射成形脱脂工艺的研究

采用粉末注射成形技术制备Ti-Mo合金吸气材料。研究了脱脂工艺对坯体质量、微观结构及其元件性能的影响。讨论了化学脱脂中的溶剂、温度、时间对坯体脱脂率的影响,较优的脱脂溶剂为三氯乙烯,在脱脂温度为50℃、脱脂时间为6h条件下,脱脂率达71.55%;通过DTA/TG曲线对热脱脂工艺进行了优化,确定了热脱脂工艺参数为室温-120℃,升温速率10℃/min;120~230℃,升温速率5℃/min;230~500℃,升温速率2℃/min,保温60 min;再经过800℃烧结工艺,制备出性能优异的Ti-Mo吸气剂元件,吸气性能特征为S10=738.5 mL/s,Q120=995.6Pa·mL。     

超细316L不锈钢粉末注射成形的脱脂工艺

采用溶剂脱脂和热脱脂相结合的方法,研究了超细316L不锈钢粉末注射成形坯的脱脂工艺。注重考察了升温速度和保温时间对不锈钢注射坯的热脱脂工艺的影响。研究表明注射成形坯经正己烷溶剂脱脂后,石蜡组元全部被脱除。其它组元在后续的热脱脂中被去除,确定了优化的升温速度和保温时间,试样没有出现缺陷,并缩短了脱脂周期,该周期大约为10小时。     

乙酸乙烯酯的单电子转移活性自由基聚合

采用SET-LRP方法进行了乙酸乙烯酯(VAc)的活性聚合。通过聚合转化率、聚合物相对平均分子量及分子量分布、聚合物核磁共振氢谱分析,研究了额外失活剂(CuCl2)、温度、溶剂等因素对聚合反应的影响。研究结果表明,失活剂CuII在使反应可控性得到增加的同时却降低了反应的转化率;反应速率不会随反应温度的升高持续增加,超过某一临界温度后反应速率反而随温度的升高而降低;与二甲基亚砜(DMSO)为溶剂相比,甲醇(CH3OH)为溶剂时,得到的聚合物的相对平均分子量较高,但分子量分布较宽。     

增塑挤压成形钨基合金棒材溶剂-热二步脱脂工艺研究

大长径比钨基合金棒材制备的关键是成形、脱脂和后续的烧结控制.基于增塑挤压成形的研究,对Ф24 mm钨基合金挤压棒坯的快速无缺陷脱脂,即溶剂-热二步脱脂工艺进行了研究.结果表明:在溶剂脱脂温度为45℃,脱脂12 h后,Ф24 mm钨基合金棒材一次脱脂率达45%;在溶剂脱指过程中增加干燥阶段,脱脂率可达70%以上;在真空气氛下对脱脂棒材进行后续热脱脂,坯体保形性好,且在12 h内,脱脂可以全部完成.采用溶剂-热二步脱脂工艺可以实现Ф24 mm钨基合金挤压棒材的快速无缺陷脱脂.     

钨合金正挤压棒坯溶剂脱脂缺陷的形成与控制

粉末挤压成形技术是制备大长径比钨基高比重合金棒材最有效的方法之一,而脱脂过程直接影响着样件缺陷控制及合金力学性能的改善效果.探讨了Φ12 mm和Φ15 mm钨基合金正挤压棒坯溶剂脱脂缺陷的形成及其控制,采用可控恒温仪调控溶剂脱脂速率,利用数码相机和扫描电镜分别对棒坯表面形貌和微观结构进行观察.结果表明：钨基合金正挤压棒...     

钛合金粉末注射成形热脱脂工艺的研究

采用粉末注射成形方法制备了钛合金坯体,然后利用溶剂脱脂方法脱除坯体中可溶性粘结剂.在热脱脂速率为2.0℃/min、最高脱脂温度600℃、保温时间为1h和真空脱脂气氛条件下脱除坯体中剩余粘结剂,坯体中残余碳氧含量分别0.092%(质量分数)和0.28%,低于国外报道的PIM钛合金脱脂坯中残余碳氧含量.XRD结果表明,脱脂坯中只存在α相,没有TiC,Ti3Al,TiO和TiN等杂质相存在.N2气氛下脱脂,脱脂坯中残余碳含量较低,但氧含量较高.     

铌合金注射成形脱脂工艺研究

设计了一种适合于铌合金注射成形的低残碳粘结剂体系,为68%PW-5%LDPE-22%PMMA-5%SA(质量分数),并研究其脱脂工艺。结果表明:脱脂时间、温度及样品厚度对溶剂脱脂率影响显著。采用三氯乙烯为溶剂,在脱脂温度为40℃,溶剂脱脂6 h,即可使粘结剂脱除率达到52.8%,使后继热脱脂时间缩短至7.5 h。以粘结剂的DSC差热分析结果为指导,可快速制定合理的热脱脂工艺,在真空热脱脂气氛条件下可使脱脂坯残余碳、氧含量得到有效控制,分别为0.18%,0.25%。     

Ti(C,N)基金属陶瓷注射成形脱脂技术研究

使用传统蜡基粘结剂和改进型蜡基粘结剂分别研究了Ti(C,N)基金属陶瓷粉末注射成形,热脱脂和溶剂脱脂 热脱脂工艺过程,其中包括根据粘结剂TGA制定并优化热脱脂的工艺曲线、不同的溶剂和温度对溶剂脱脂的影响、后续热脱脂工艺路线的确定.结果表明:使用改进型蜡基粘结剂的2#试样热脱脂工艺简单、周期短并易于控制;2#溶剂脱脂率明显高于使用传统蜡基粘结剂的1#试样;经过溶剂脱脂 热脱脂,1#试样脱脂率达到93%,2#试样脱脂率达到96%以上;1#烧结试样的抗弯强度为700 MPa左右,2#则达到1300 MPa,从烧结样品抗弯断口和显微组织的SEM图片得到了验证.Ti(C,N)基金属陶瓷注射成形采用改进型蜡基粘结剂比传统蜡基粘结剂脱脂效果好、力学性能高,改进型蜡基粘结剂更适合Ti(C,N)基金属陶瓷注射成形.     

MIM石蜡基热塑性粘结剂的流变学性能和脱脂性能

研究了具有不同聚合物组元的几种石蜡基粘结剂和喂料的流变学性能的脱脂性能,比较了聚合物组元件其流变学性能,脂性能及产品力学性能和尺寸收缩性能的影响。结果表明,采用ＨＤＰＥ和ＥＶＡ作为聚合物组元的ＰＷ－ＨＤＰＥ－ＥＶＡ粘结剂具有最优性能。     

金属注射成形蜡基粘结剂的研究

本文研究了综合蜡基和油基粘结剂优点的改进型蜡基粘结剂体系 ,其组成为PP PW 植物油 SA 改性剂。改进型蜡基粘结剂分阶段热解 ,各组元间有较强的相互作用 ,相容性较好。该粘结剂和金属粉末具有较好的混合均匀性 ,改性剂的加入提高了粉末装载量。喂料是一种假塑性流体 ,非牛顿指数n较大 ,粘流活化能ΔEη 较低 ,具有良好的注射填充性。改进型蜡基粘结剂既可热脱脂 ,又可溶剂脱脂 ,溶剂脱脂速度快、维形能力好。     

Thermal, Solvent, and Vacuum Debinding Mechanisms of PIM Compacts

The mechanisms of thermal, solvent, and vacuum debinding processes for powder injection molded (PIM) compacts were investigated. Mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) observations on PIM specimens showed that fine interconnected pores were developed in the early stages of debinding in all three processes. These pores were formed as a result of the decomposition of low temperature binders such as paraffin wax during thermal debinding or arise from the extraction of soluble binder components in solvent debinding. In the later stages of thermal and vacuum debinding, decomposed gases could be trapped in the center region and build up a pressure causing cracking or blistering defects. The solvent debinding process could alleviate these problems, but the penetration of solvent into the binder could still cause cracking or distortion due to swelling of the binder.

It was found that the pore structure evolution was influenced by the heating rate, temperature, pore size, and the amount of existing porosity. From the observed microstructure and mercury porosimetry data, debinding mechanisms were derived and the defects which were frequently seen during debinding were explained with these mechanisms.     

Scientific and Technological Progress in Binder Burnout from Metal Injection Molded Compacts

A two-component model binder system composed of the low molecular weight component stearic acid (SA) and the polymer polypropylene (PP) was chosen to study the kinetics of long-term conventional thermal debinding of SA from a metal powder compact formed from spherical stainless steel powder. The burnout temperature of the two binder components is widely different, so that the SA-weight loss could be followed in the lower temperature regime independently by thermogravimetric analysis. The experiment provides at constant temperature an exponential decrease of the SA-weight with debinding time. It is suggested that the debinding rate is controlled by diffusion of SA in the thermoplastic to inner surfaces of pores, which develop in the material during debinding. This is in correspondence with previous work on short-term debinding. The kinetics for the PP/SA-system are compared to previous results on binders with other polymer components. The second part of this paper reports about MIM-processing of commercial steel parts with a novel proprietary binder formulation which allows a distortion-free conventional thermal debinding within hours.     

新型金属注射成形催化脱脂型粘结剂的催化快速分解研究

催化脱脂是目前MIM技术领域新的发展方向,研究了新型金属注射成型催化脱脂型粘结剂的催化快速分解,研究结果表明,该催化脱脂型粘结剂在以HNO3为催化剂进行催化脱脂时,注射成形坯经3－4h催化脱脂后,脱脂坯内部已形成大量的连通孔道,脱脂时间,脱脂温度以及 不同粘结剂组成影响催化脱脂效果。     

Effects of debinding parameters on powder injection molded Ti-6Al-4V/HA composite parts

Titanium alloy-hydroxyapatite(Ti-6Al-4V/HA) composite powders produced by a ceramic slurry were mixed with a multi-component binder system in the powder injection molding process. The binder system comprises mainly of natural wax, fatty acid wax, stearic acid, poly-oxialkyen-etherand olefln-hydrocarbons. After molding, the binder system was removed by conventional thermal debinding. The effects of heating rate and gas flow rate on the quality of the debound part in terms of defects, mass of binder removed and residual carbon level were discussed. A slow heating rate (20° C/h) at the beginning stage of the debinding step and a higher gas flow rate (250 cm³ /min) were required for the production of defect-freeparts with minimal carbon level.     

Injection moulding of alumina with partially water soluble binder system and solvent debinding kinetics

Abstract

A partially water soluble binder system was successfully derived and tested for injection moulding of alumina powder. The major binder of the binder system was comprised of poly(2-ethly-2-oxaline) and polyethylene glycol and these constituents formed the water soluble fraction of the system. The rheological properties of the feedstock were investigated systematically over a temperature range of 120 to 160°C and a shear rate range of 100 to 1000 s^?1. Binder removal was accomplished using a two stage process. The water soluble constituents were removed by water leaching. The remaining binder constituents were removed by thermal pyrolysis. The solvent debinding kinetics of the water leaching process were studied as a function of temperature, ranging from 40 to 80°C. Solvent debinding is a two stage process consisting of dissolution and diffusion. In this study, dissolution was the rate limiting step during the first stage of water leaching over a leaching time of 90 min at 40°C. As the process proceeds, it is shown that diffusion becomes the rate limiting step.     

Development of Novel Binder for Hardmetal Powder Extrusion Molding

A novel binder system for hardmetal powder extrusion moulding(PEM) process has been developed.The binder system comprises a major fraction of a mixture of low molecular weight components (LMWCs) and a minor fraction of very finely dispersed polymer.The feedstocks are mixed as a thick slurry at a suitable temperature and are rapidly homogenized by stirring at an adequate shear force.The binders are removed by thermal debinding.The thermal debinding mechanism has been investigated by thermogravimetry(TG) and differential thermogravimetry(DTG).At the first stage of debinding,the LMWCs are removed.These open up pore channels which allows much faster removal of the remaining polymer component during the subsequent stage.Ihe microtructures of the moulded green parts were observed by scanning microscopy(SEM).The debound samples were sintered at different temperatures,and the sintered samples properties were measured.