Binder Removal Rate Research Articles

Formulating titanium powder feedstocks for metal injection moulding from a clean binder system

Impurity control is paramount in achieving success in titanium metal injection moulding (Ti-MIM), primarily due to Ti being a universal solvent for interstitial elements such as oxygen and carbon. This study developed a clean binder system with a low decomposition temperature based on polypropylene carbonate/polyoxymethylene (PPC/POM). However, due to the poor shape retention of the PPC/POM binder system, polyethylene glycol (PEG) was incorporated to facilitate the formation of a porous network within the compact structure, allowing efficient removal of residual binder for subsequent debinding process. The results reveal that increasing the PEG content leads to a higher binder removal rate, while adding POM enhances shape retention during debinding. The optimal PEG/PPC/POM binder system compositions were identified as 40/48/10% w/w, respectively, offering a higher PEG removal rate and improved shape retention. Lastly, the resultant debound titanium feedstock from this novel binder system showed low impurity contents, complying with ASTM F2989 requirements.

Determination of wear parameters and mechanisms of diamond/copper tools in marble stones cutting

In this paper, a type of soft metal binder of diamond tools (diamond segments) that was consisted of 78% Brass (Cu-10Zn) +16% Bronze (Cu–10Sn) + %6Co was investigated. The first, it was approved that the binder is a soft metal binder by a hardness test for diamond tools in natural stones cutting. Then, the effective factors on grinding efficiency such as specific energy (SE), Cutting force (FC), metal binder removal rate (MRR), grinding ratio (G-ratio), wear resistance and Mean free path (MFP) were evaluated by different formula and equations. On the other hand, the effect of different wear mechanisms on the metal binder and diamond grits of the tool was evaluated by the cutting of a type of very hard marble stone that calls Cappochino Beige Marble (CBM). The existence of wears of abrasive, surface fatigue, impact and erosive were confirmed by scanning electron microscopic observations. According to hardness 73 HRB (hardness of the binder) and the wears, there is a short tools life for the diamond tool due to low wear resistance of the metal binder but, the cutting rate was high. Novelty statementThe rising price of decorative stones will increase the final price of the stones and will overshadow the global market of decorative stones. The presence of cobalt, iron, chromium and nickel powders increases the price of diamond tools because of their high price. On the other hand, due to the higher temperature and time of hot press to produce these tools by the mentioned powders, it will also increase the price. Therefore, in this paper, brass and bronze alloy powders, which are much cheaper than cobalt, iron, chromium and nickel powders, have been used as main metal binder powders to reduce raw material prices and manufacturing process costs. On the other side, due to the creation of a softer metal binder compared with the more expensive and harder binder of cobalt, iron, chromium and nickel powders, it can be affected to increase the cutting speed because of increasing wear of the binder. Therefore, mathematical calculations are essential for the efficiency of the tools' cutting.

Binder removal by a two-stage debinding process for powder injection molding Fe–50Ni alloy parts

Debinding is a critical process for injection molded green parts of soft magnetic materials. In case of incomplete binder removal, the residual impurities deteriorate the magnetic performance of the final components. On the other hand, binder decomposition reduces the structural strength of the green parts. Therefore, it is important to engineer an appropriate debinding cycle not only to ensure efficient binder removal but also to retain the structural strength of the parts. In this study, the two-stage debinding process is optimized focusing on the higher rate of binder removal to get defect-free parts. The feedstock of Fe–50Ni alloy with a multicomponent binder system was prepared followed by injection molding. In the first stage, the binder was removed by solvent debinding and in the second stage, thermal debinding was carried out. The various types of defects were observed during debinding process. It has been found that efficient solvent debinding extracted 98% binder whereas thermal debinding at a heating rate of 2 °C min−1 results in defect-free quality parts.

Debinding Rate Enhancement of 17-4 Precipitation Hardening Stainless Steel Solvent Debinding on Metal Injection Molding Process as the Material for Orthodontic Bracket

Brackets fabrication should be done by a suitable process to produce great result. Processes commonly used are investment casting, machining, and metal injection molding. Investment Casting has a drawback in which the surface roughness is quite high for the standard of brackets and require further processing. Machining is done by removing unwanted part to get desire shape, whereas bracket shape requires a high accuracy and is quite complicated. In Metal Injection Molding, feedstock is injected into a mold where complicated shapes can be achieved with a better surface roughness. The weakness is the stages within the process are quite long. One of the problem is the efficiency of debinding stage. We conducted an experiment to enhance binder removal rate through solvent debinding with stirring and under vacuum condition. Sample use for this experiment is a cubic shape of 0.5 x 0.5 x 0.5 cm3. Experiment is done on magnetic stirrer and in vacuum furnace. The temperature is hold at 50°C. Drying process afterward is done in the vacuum furnace for 1 hour with temperature around 50°C. Amount of binder left is confirmed by STA and the particle morphology is seen by SEM. Results showed that stirring treatment enhances binder removal rate due to stirring mechanism that causes possibility of collisions between particles increases. Binder removal rate on the vacuum treatment has a mechanism similar to stirring, but with the addition of the solvent to be done on a regular basis due to decrease of solvent boiling point under vacuum. There were no cracks found on the surface with an increased rate of debinding. Stirring is use for experiment with sample of actual bracketorthodontic form. Debinding rate of the bracket sample is faster than the cubic sample. This result is affected by the dissimilarity on the volume to surface area.

Characterisation of NiO-YSZ Porous Anode-Support for Solid Oxide Fuel Cells Fabricated by Ceramic Injection Moulding

Ceramic injection moulding (CIM) has advantages for a cost effective fabrication of large-scale, near-net-shape products. In this work, CIM is carried out to prepare porous anode-support for solid oxide fuel cells (SOFC) applications. The CIM process started with a preparation of feedstocks by mixing powder with binder. The feedstock is then injected into the mould of desired shapes. The mouldings were subsequently undergo the removal of the binder (debinding) and, finally, sintering. It is shown that porous nickel oxide-yttria stabilized zirconia (NiO-YSZ) anode-support for SOFC were successfully prepared by CIM technique. In addition, a water-soluble based binder system, consisted mainly of polyethylene glycol (PEG), has been used in this work. This is to avoid the use of organic solvents when wax-based binder was used. Therefore, it can promote more environmentally friendly process. The removal of binder was carried out using water debinding technique. The porous anode for SOFC was subjected to systematic characterisation. The effect of processing parameters, such as powder characteristics and powder/binder ratio has been investigated. Rate of binder removal was also studied. The porous anode specimens were characterised for their properties and microstructure. It was also found that the porosity of the specimens can be controlled by adjusting the sintering temperatures and holding times.

RETRACTED ARTICLE: Optimisation of compositions of PEG/PMMA binder system in ceramic injection moulding via water debinding

In this study, we have made a comprehensive investigation on the optimisation of the compositions of polyethylene glycol (PEG)/polymethyl methacrylate (PMMA) binder system for water debinding. An orthogonal test was designed, and L9(33) table was chosen to investigate the influence of the molecular weight of low molecular PEG (L-PEG), high molecular PEG (H-PEG) and the percentage of L-PEG in PEGs on flaws of the injection moulded compacts after water debinding. In addition, the ratio of PMMA content to PEG content on flaws is also investigated. Four regions were defined as high stress region, safe debinding region, low binder removal rate region and unavailable injection region respectively. It is believed that our work could provide comprehensive and convincing principles for the manufacturing of injection moulded ceramic parts via water debinding.

Influence of Specimen Dimensions and Temperature on the Debinding Behavior of Alumina Feedstock

This work investigated the influence of specimen dimensions and temperature on the debinding behavior of alumina feedstock for powder injection process. Polyethylene glycol (PEG) was used as a based binder. It is soluble in water therefore the use of wax-based binder system can be avoided. PEGs with a molecular weight of 1500 and 4000 were mixed with polyvinyl butyral (PVB) a minor component. Stearic acid was added during feedstock preparation to act as a lubricant. Debinding process was carried out using a water leaching test at 30 and 70 °C to study for PEG removal rate. Specimens retained their shapes after leaching of the binders. In general, the rate of binder removal increased at initial stage then slowed down at longer leaching times. A faster debinding rate was achieved at 70 °C when compared to 30 °C. In addition, samples with a higher surface area to volume ratio (As/V) led to an increase in the %PEG removal rate. This study also showed the relationship between %PEG removal as a function of different surface area to volume ratio (As/V) which can be helpful in predicting %PEG removal for any other samples having cylindrical shape.

Binder removal via a two-stage debinding process for ceramic injection molding parts

Debinding binders in two stages is critical to maintaining the shape of injected parts; the resulting decomposition affects the strength and rigidity of a structure. This study determines the optimal debinding process on the basis of a higher binder removal rate and the production of defect-free parts. The feedstock used was a combination of alumina–zirconia powder with a binder that consists of high-density polyethylene (HDPE), paraffin wax (PW), and stearic acid (SA). During the first stage, the injected parts were immersed in an n-heptane solution at 50°C, 60°C, 65°C, and 70°C to remove PW and SA. Binder weight loss was evaluated as a function of time. In the second stage, HDPE was removed by using thermal debinding. The results show that the optimum solvent debinding process runs for 16h at 60°C. The weight loss of the binder reaches 41.1% and results in the formation of defect-free parts. The binders are degraded at approximately 550°C during thermal debinding. This degradation resulted in decomposition of nearly 96.9% of the binders. Low heating rates (1°C/min to 2°C/min) prevent defects from forming in the injected parts.

Optimization of the Compositions of PEG/PMMA Binder System in Ceramic Injection Moulding via Water-Debinding

In this study, we have made a comprehensive investigation on optimization of the compositions of PEG/PMMA binder system for water-debinding. An orthogonal test was designed and L9(33) table was chosen to investigate the influence of the molecular weight of low molecular PEG (L-PEG), high molecular PEG (H-PEG) and the percentage of L-PEG in PEGs on flaws of the injection moulded compacts after water-debinding. In addition, the ratio of PMMA content to PEGs content on flaws is also investigated. Four regions were defined as high stress region, safe debinding region, low binder removal rate region and unavailable injection region respectively. It is believed that our work could provide comprehensive and convincing principles for the manufacturing of injection-moulded ceramic parts via water-debinding.

Debinding of stainless steel foam precursor with 3-D open-cell network structure

The thermal debinding behavior of stainless steel foam precursor in vacuum was studied and compared with that in hydrogen. The formation cause of pore channel was analyzed. The experiment results show that the binder removal rate in vacuum is higher than that in hydrogen. In vacuum, the organic compounds can be removed effectively without change of pore size and the pore morphology for the sample. After pre-sintering, some sintering necks form and the sample has certain intensity. The initial surface pore forms with the temperature increasing at first, and then the internal melting binder is aspirated to form initial pore because of the capillary force and the metal powders re-arrange with the migration of binder at the same time.

Removal of Paraffin Wax Binder from Metal Injection Molded Part by Supercritical Fluids

The metal injection mold (MIM) process is the most cost effective, highest quality means to produce complex shaped, high performance parts. In the MIM process, debinding is a key step for successful MIM. However, the conventional debinding processes, which are thermal debinding and solvent debinding, have disadvantages that include long product development times, and harm to the environment. Therefore, the study of supercritical CO2 that can be used as solvent for debinding, a new debinding technology as substitute for a conventional technology, was considered. In this paper, we used two methods to investigate a method for reducing debinding time as well as lowering operation condition other than pure supercritical CO2 debinding: the first method was to add cosolvent in supercritical CO2, the second method was to use the mixture of propane + CO2, as the supercritical solvent. It was found that the addition of cosolvents and the use of binary mixture propane + CO2 for supercritical solvent remarkably improved the binder removal rate, in comparison with using pure supercritical CO2.

Thermal debinding processing of 316L stainless steel powder injection molding compacts

The process of thermal debinding of injection molded water atomized 316L stainless steel powder compacts was studied in a vacuum and hydrogen atmosphere using a mercury porosimetry and the thermogravimetric analysis method. The vacuum debinding rate was investigated under the conditions of different binder compositions and temperature-increase rates, especially at the low temperature stage. The process of thermal debinding in the hydrogen atmosphere was compared with that in vacuum. It was found that the binder removal rate was much higher in vacuum than that in the hydrogen atmosphere under the same experimental conditions. The mercury porosimetry was used to measure the pore structure evolution. The results of the mercury porosimetry indicated that the pore structure evolution in injection molded compacts during thermal debinding in vacuum was greatly different from that in hydrogen atmosphere. A fine inter-connected pore structure developed as a result of the evaporation and removal of the low molecular binder components at the early stage of debinding. The reason for the difference in binder removal rate and the inter-connected pore structure in these two debinding environments lies in the difference of the vapor pressure drop, which was the vapor pressure difference between that in the molded compacts and that in the ambient environment. At the different thermal debinding stages and environments, the pore structure evolution and changes in the mean pore size in the thermally debound compacts were also different. From the low debinding temperature stage to the intermediate temperature stage of about 300 °C, the pores in the thermally debound compacts in the hydrogen atmosphere were finer and the pore size distribution was more homogeneous than that in the vacuum. At the final debinding stage, the pore size distribution was almost the same in the hydrogen atmosphere as in the vacuum.

분말사출성형에서 초임계유체를 이용한 탈지공정

The purpose of the present study is to investigate the method decreasing debinding time as well as lowering operation condition than pure supercritical <TEX>$CO_2$</TEX> debinding by using cosolvent or binary mixture of propane + <TEX>$CO_2$</TEX>. First method is to add cosolvent, such as n-hexane, DCM, methanol, 1-butanol, in supercritical <TEX>$CO_2$</TEX>. In case of adding cosolvent, we were found the addition of non-polar cosolvent (n-hexane) improves dramatically the binder removal rate (more than 2 times) compared with pure supercritical <TEX>$CO_2$</TEX> debinding, second method is to use mixture of supercritical propane + <TEX>$CO_2$</TEX>, as solvent. In case of using mixture of supercritical propane + <TEX>$CO_2$</TEX>, the rate of debinding speeded up with increasing of pressure and concentration of propane at 348.15 K. It was found that addition of cosolvent (e.g., n-hexane, DCM) and binary mixture propane + <TEX>$CO_2$</TEX> for supercritical solvent remarkably improved binder removal rate for the paraffin wax-based binder system, in comparison with using pure supercritical <TEX>$CO_2$</TEX>.

Supercritical Carbon Dioxide debinding in metal injection molding (MIM) process

The conventional debinding process in metal injection molding (MIM) is critical, environmentally unfriendly and time consuming. On the other hand, supercritical debinding is thought to be an effective method appropriate for eliminating the aforementioned inconvenience in the prior art. In this paper, supercritical debinding is compared with the conventional wicking debinding process. The binder removal rates in supercritical CO2 have been measured at 333.15 K, 348.15 K, and 358.15 K in the pressure range from 20 MPa to 28 MPa. After sintering, the surface of the silver bodies were observed by using SEM. When the supercritical CO2 debinding was carried out at 348.15 K, all the paraffin wax (71 wt% of binder mixture) was removed in 2 hours under 28 MPa and in 2.5 hours under 25 MPa. We also studied the cosolvent effects on the binder removal rate in the supercritical CO2 debinding. It was found that the addition of non-polar cosolvent (n-hexane) dramatically improves the binder removal rate (more than 2 times) for the paraffin wax-based binder system.

A diffusion-controlled kinetic model for binder burnout in a powder compact

Many powder metallurgy processes involve the use of a polymeric binder as a carrier for easy manufacture of product pre-forms. Complete and clean removal of the binder before consolidation or firing is essential to achieve high quality materials or products. A diffusion-controlled numerical model was established here for the prediction of binder burnout kinetics within powder compacts. It considers the degradation of a polymeric binder into a monomer, liquid state diffusion of the monomer in a core region, and gaseous transport of the monomer in a gas-filled annulus. The rate-controlling mechanism is identified as the diffusion of the monomer in the liquid core, while gaseous transport in the porous annulus poses minor influence. The model is able to predict the remaining weight fraction of polymer during debinding and the total burnout time under different geometric and processing conditions. It is noted that the burnout time increases markedly with compact size, but varies insignificantly with powder particle size. The rate of binder removal increases sharply with temperature. The theoretical predictions of the burnout-out kinetics are in line with experimental findings.

Thermal removal of multicomponent binder from ceramic injection mouldings

Thermal removal of polymer binder containing low-molecular-weight components from ceramic injection mouldings was studied. The effect of the shape and size of bodies on the process of binder removal was examined. Evaporation of low-molecular-weight components represented the most important process at the beginning of binder removal. It was found that a bed of activated carbon speed up removal of low-molecular-weight components. The mechanism of binder removal in a bed of activated carbon was described. Binder redistribution and evolution of porosity in the body during binder removal was investigated. A high rate of binder removal resulted in non-uniform binder distribution in the body. The formation of defects due to non-uniform binder removal was described and requirements for their elimination were proposed.

Effect of Activated Carbon Bed on Binder Removal from Ceramic Injection Moldings

Weight losses during the binder removal from ceramic injection moldings that have been placed in beds of activated carbon powder and two types of alumina powder were compared. The effect of the specimen size and shape on debinding in a bed of activated carbon was investigated. Because of the structure of its particles, activated carbon powder allowed binder losses in ceramic moldings that consisted of submicrometer-sized particles to increase at a temperature of 130°C. The binder loss in a bed of activated carbon was dependent on the ratio of surface area to volume of the body that was extracted. Renewal of the sorption abilities of the bed of activated carbon after saturation with binder increased the rate of binder removal.

Thermogravimetric and binder removal analysis of injection moulded reinforced ceramic composite

The study of the binder removal processes for injection moulded ceramic composite compacts was studied with the aid of a thermogravimetric analyser. It has been observed that a number of factors, such as the heating rate, the heating environment and the heating profile have an effect on the rate of binder removal. The matrix of the composite was alumina and the reinforcement was silicon carbide whiskers. It was confirmed that the presence of silicon carbide whiskers in the injection moulded compacts provided additional oxygen diffusion paths to enhance oxidative degradation. It was also found that the heating profile used for binder removal had a strong influence on the formation of internal cracks in the moulded components.