Comparative study of pore structure evolution during solvent and thermal debinding of powder injection molded parts

Hwang, K. S.; Hsieh, Yi-Chien

doi:10.1007/bf02648403

Cited by 51 publications

(28 citation statements)

References 7 publications

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“…A proper debinding process is necessary to avoid defect formation (Hwang and Hsieh 1996). Several debinding methods were tested on the 26 vol.% feedstock, as depicted in Fig.…”

Section: Debindingmentioning

confidence: 99%

Micro injection molding of micro gear using nano-sized zirconia powder

Fuh

et al. 2008

Microsyst Technol

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Powder injection molding (PIM) is well established in macro molding. Scaling down to micro-PIM (lPIM) opens a new arena for cost effective production of micro components. One potential application is the manufacture of cutting tools with sharp edges for machining. However, scaling down to such a level produces challenges in raw material preparation, injection molding and thermal treatment. In this report, near dense ([98% of theoretical density) tensile bars and 3 mm micro gears were produced using 50 nm Yttria Tetragonal Zirconia Polycrystal (Y-TZP). The sintered gear teeth were well defined and visually defect free.

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“…A proper debinding process is necessary to avoid defect formation (Hwang and Hsieh 1996). Several debinding methods were tested on the 26 vol.% feedstock, as depicted in Fig.…”

Section: Debindingmentioning

confidence: 99%

Micro injection molding of micro gear using nano-sized zirconia powder

Fuh

et al. 2008

Microsyst Technol

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“…In this case, the lack of binder movement control would lead to non-constrained particles, due to the decrease in the solid percentages at the surfaces, and a layer rich of binder could be formed; consequently, after debinding. In addition, other phenomena could occur such as the outward flow, where the binder sometimes; as a result of the high negative capillary pressure at these areas, tend to sweeps and fills all the contacts and fine pores [5]. The final stage- of the process is reached when binder decomposition occurs at the outer edges, which would lead to an increase of volume in large inter-particle pores; at the same time, another binder decomposition takes place at inter-particle contacts and fine pores, resulting in a somewhat smaller mean pore size.…”

Section: Resultsmentioning

confidence: 99%

“…Binder-assisted forming techniques are considered, nowadays, an important potential address of research in the area of powder processing. One of the most important techniques is the powder injection molding (PIM), which is based on using a closed die to form the powder into a desired shape using a thermoplastic polymeric material [1][2][3]; therefore, it is a combination of conventional plastic molding and powder metallurgy, which benefits from each in easy shaping and superior mechanical properties, respectively [4][5]. PIM, as a forming technique for high temperature alloys, has been paid great attention due to its high potential for producing complex shapes with large quantities and at low cost [6].…”

Section: Introductionmentioning

confidence: 99%

Comparative study of different alloys during thermal debind-ing of powder injection molded parts

El-Garaihy

Nassef

El-Hadek

2016

IJET

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Powder injection molding (PIM) is an interesting technique and address of research, in which a thermoplastic polymeric material is used to form the powder into the desired shape in a closed die. Binders have a crucial importance in the powder metallurgy technology as they play a vital role to provide efficient powder agglomeration and/or lubrication during shaping. At the same time, they have to be easily removed from the compacts during initial stages of sintering, using debinding process, without any damaging effect for the base material. Thermal debinding is a vital process requiring somewhat elevated temperatures to remove binder from the compact. In the current study, an investigation has been made about the effect of process variables on the debinding of injection molded pieces, by melt wicking. The debinding process was performed at temperatures ranging from 160-up to-200°C for a time duration varying from 1-up to-27 hours. All powders used in injection molding feedstock have an inherent packing porosity. Several types of alloy powders (Carbonyl iron steel, Nickel aluminide, and 316L stainless powders), with various size distributions, particle shapes, and materials are adopted to define the influence on binder incorporation resulted from this inherent porosity. Results revealed that the increase of debinding time or decrease in the wicking powder (alumina) particle size lead to an increase in the thickness of the adhered layer of alumina. When the wicking powder is very fine (0.3 m) or has a wide particle size range (<10 m), it becomes more dense and its debinding efficiency is decreased. At high debinding temperatures (200 °C) the rate of binder evaporation and removal increased, which leads to decreasing the cohesion of the samples yielding a shape distortion. In addition, the effect of the wicking powder (Al 2 O 3 ) sizes and debinding time on the binder weight loss percentage after debinding process for FeOX, Ni 3 Al, and 316L has been investigated.

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“…Because 2n 1 r 1 ϭ 2n 2 r 2 ϭ L/2, where L is half the thickness of the specimen, the diffusion lengths obtained from Eq. [2] for coarse and fine powders are the same and are equal to и L/6. This finding indicates that the critical factor that determines the debinding time is the cross-section thickness.…”

Section: Discussionmentioning

confidence: 98%

“…[1] To understand the solvent rebinding behavior, Hwang and co-workers examined the microstructure evolution of powder injection molded (PIM) compacts and the interaction between the binder components and the solvent during debinding. [2,3] It was shown that pore channels develop and the average pore size increases as the debinding proceeds. These pore channels provide paths for the dissolved solution to diffuse out of the compact.…”

Section: Introductionmentioning

confidence: 99%

Solvent debinding behavior of powder injection molded components prepared from powders with different particle sizes

Hwang

Shu

Lee

2005

Metall Mater Trans A

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It is generally accepted that the solvent debinding rate of powder injection molded (PIM) parts can be improved when coarse powder is used due to the larger pore size present in the compact. However, little hard experimental evidence on this has been reported. In this study, the as-received gas-atomized stainless steel powder was classified into four different particle sizes. Little difference in the debinding rate was found among these four groups. Similar results were also obtained using classified fine carbonyl iron powder and coarse water atomized iron powders. The diameter of the pore channel that was developed in the compact, while increasing as the particle size increased for both iron and stainless steel powders, did not affect the debinding rate. A comparison between the sizes of the pores and diffusing molecules suggests that the pores are significantly large for the small diffusing molecules. The calculation of the diffusion path or torturosity also indicates that the particle size does not affect the diffusion length and thus not the debinding rate.

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Comparative study of pore structure evolution during solvent and thermal debinding of powder injection molded parts

Cited by 51 publications

References 7 publications

Micro injection molding of micro gear using nano-sized zirconia powder

Micro injection molding of micro gear using nano-sized zirconia powder

Comparative study of different alloys during thermal debind-ing of powder injection molded parts

Solvent debinding behavior of powder injection molded components prepared from powders with different particle sizes

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