Papers by Keyword: Powder Injection Molding (PIM)

Abstract: This research presents the effects of temperature and cooling rate on mechanical properties of powder injection molded 316L Stainless steel. Steel powder and binder were mixed together to produce the feedstock. The green samples were produced by injection molding and debinded. Brown test samples were sintered in vacuum at 1325°C, 1360°C and 1380°C for 2h with two heating and cooling rates 5°C/min and 10°C/ min. The test samples sintered at 1325°C achieved maximum sintered density. The higher cooling rate improved the strength of the sintered test samples. The maximum sintered density of 96% and tensile strength of 503MPa was achieved and these results are comparable to the wrought 316L stainless steel (according to ASTM standard).

Abstract: In this study, metal composite feed stocks were prepared and test samples were produced by powder injection molding and Multiple Live-Feed Molding (MLFM) devices to investigate the effects of fiber content and macro-shear on the fiber fracture. Fiber-length was measured using an image processing system. The results showed that the fiber volume content increased fiber fracture by 9% and viscosity showed 10% increase in fiber fracture. Samples produced by MLFM devices showed a 1% higher fiber fracture compared to the test bars produced by injection molding. Tensile strength of composites was calculated using fiber contents and fiber length. Considerable increase in tensile strength was noted for metal composites with fiber length above a critical length.

Abstract: The quality of the green and the shaping efficiency are affected by the mold structure during the course of powder injection molding (PIM). Based on the numerical simulation, the mathematic model for the optimal design of the gating and runner system in PIM mould is constructed. The method is testified by the Moldflow software and the experiment. From the result, it is suggested that the clamp force and the shape cycle are clearly decreased, the green is densified and the samples’ density error of the green is decreased after the optimal design of the mold structure. Furthermore, the number of trial mold is reduced and the shape efficiency is improved.

Abstract: Binders based on mixtures of polymers and waxes are suitable both for solvent combined with thermal extraction, as well as for pure thermal debinding. The recently developed plasma-assisted debinding and sintering (PADS) process has been targeted, for historical reasons, on a wax-polymer system, appropriated for solvent combined with thermal extraction processes. This paper shows experimental results related to the debinding rate of parts produced by metal powder injection molding using the recently developed Plasma Assisted Debinding process. Influence of temperature and the ratio of cathodic area on the mass loss were studied.

Abstract: There are various methods for testing the viscosity of MIM feedstocks and described in the literature, e.g. melt-indexer, capillary viscosimeter, etc. Typical factors taken into consideration for choosing a proper method for feedstock characterization are the costs and the time needed for measuring. The paper presents three methods which have been developed to check the feedstock consistency directly on the injection molding machine. The first method is based on a slit-die rheometer. The second method considers the energy which is needed for conveying the melt inside of the plastification unit. And the third method is similar to a melt indexer but also in this case the measurement is done directly on the injection molding machine. These novel methods are suitable to detect inconsistencies in feedstock preparation.

Abstract: Research on determined alloys produced by metal injection molding has been done for cost reduction purposes through the use of powders with bigger particle size. However, regarding feedstock homogeneity, certain limitations are presented when coarse particles are used. For instance, homogeneity strongly influences rheological behavior of the feedstock and dimensional control of the sintered part. Therefore, the purpose of this work was to evaluate effectiveness of a modified binder system with the addition of a surfactant polymer which makes the feedstock more homogeneous. This study was carried out on a FeNiP alloy currently processed by MIM, where 50%wt of the iron powder was replaced with course powder having a particle size distribution of D90 less than 47 ,m. Effectiveness of binder systems using a Melt Flow Index (MFI) and the behavior of dimensional accuracy at sintered part were analyzed. Results showed more feedstock homogeneity and less dimensional deviation when a surfactant agent was used.

Abstract: Ni-Fe based soft-magnetic alloys, processed via Metal Injection Molding (MIM), were investigated regarding the influence of processing route on final magnetic properties and compared to fully dense cast materials. The process variations included high and low temperature debinding, different sintering routes and the application of hot isostatic pressing (HIP). The different densities resulting from the process variations were related to maximum magnetic permeability. Results have shown that density, in the range between 7,5g/cm³ and 8,0g/cm³, does not have significant influence on the maximum permeability, allowing cost-effective process routes. It was also verified that fullydense cast alloys still exhibits superior properties, with lower coercive fields and higher permeability, but results achieved after HIP process overcame even the values of these commercial grade alloys.

Abstract: Powder injection molding (PIM) process was applied to Fe-based metamorphic alloy powders, and microstructure, hardness, and wear resistance of the PIM products were analyzed and compared with those of conventional PIM stainless steel products. When Fe-based metamorphic powders were injection-molded and then sintered at 1200 oC, completely densified products with almost no pores were obtained. They contained 34 vol.% of (Cr,Fe)2B borides dispersed in the austenitic matrix without amorphous phases. Since these (Cr,Fe)2B borides were very hard and thermally stable, hardness, and wear resistance of the PIM products of Fe-based metamorphic powders were twice as high as those of conventional PIM stainless steel products. Such property improvement suggested new applicability of the PIM products of Fe-based metamorphic powders to structures and parts requiring excellent mechanical properties.

Abstract: Powder injection moulding (PIM) is a cost effective powder metallurgical process for the fabrication of small, complex-shaped components for high performance applications. A binder system, which comprises a major fraction of polyethylene glycol (PEG) and a minor fraction of a very finely dispersed polymethyl methacrylate (PMMA), has been applied for tungsten carbide (WC) – cobalt (Co) hardmetal powders. PEG can be removed rapidly by water leaching and PMMA is removed by subsequent pyrolysis when the components are ramped up to the sintering temperature. In this work, the development of feedstock formulations and of the processing parameters for a successful injection moulding and to achieve high density has been investigated. The present study has demonstrated that the binder can be employed for the production of WC-Co hardmetal components by PIM process. The maximum density achieved thus far is 97% of the theoretical value.

Abstract: Processing and properties of a dome-shaped piezoelectric transformer with a composition of 0.03Pb(Sb0.5Nb0.5)O3-0.03Pb(Mn1/3Nb2/3)O3-0.465PbTiO3-0.475PbZrO3 have been investigated. A dome-shaped sample was fabricated by powder injection molding. The dimension of the dome-shaped sample was a 28 mm in diameter and 2.1mm in thickness with a curvature radius of 18 mm. Finite element modeling for the complicated piezoelectric transformer was applied to simulate vibration mode in the sample. The high power characteristics of a dome-shaped piezoelectric transformer were examined by the lighting test for a 55W PL lamp. The 55W PL lamp was successfully driven by the dome-shaped piezoelectric transformer with sustaining efficiency higher than 98%. The transformer with ring/dot area ratio of 2.1 exhibited the maximum properties in terms of output power, efficiency and temperature stability.