Progress in Powder Metallurgy

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Authors: Francis Hanejko, Arthur Rawlings, Patrick King, George Poszmik
Abstract: This paper will describe a powder and processing method that facilitates single presssingle sintered densities approaching 7.5 g/cm³. At this sintered density, mechanical properties of the powder metal (P/M) component are significantly improved over current P/M technologies and begin to approach the performance of wrought steels. High performance gears have the added requirement of rolling contact fatigue durability that is dependent upon localized density and thermal processing. Combining high density processing of engineered P/M materials with selective surface densification enables powder metal components to achieve rolling contact fatigue durability and mechanical property performance that satisfy the performance requirements of many high strength automotive transmission gears. Data will be presented that document P/M part performance in comparison to conventional wrought steel grades.
Authors: Chong Xi Bao, Zhou Qiang Shen, Zheng Ping Shu
Abstract: The processes of P/M affect the properties of sintered gears. The different techniques of P/M lead to the different properties of sintered gears. This paper summarizes new progress in powder metallurgy for sintered gears. These progresses include warm compaction, high velocity compaction, sinter hardening, high temperature sintering, infiltration, CNC powder press and surface densification etc.
Authors: Jose Manuel Prado
Abstract: In this work the elastic behaviour of metallic powder compacts is studied. Cylindrical specimens with different levels of density have been submitted to uniaxial compression tests with loading and unloading cycles. The analysis of the elastic loadings shows a non linear elasticity which can be mathematically represented by means of a potential law. Results are explained by assuming that the total elastic strain is the contribution of two terms one deriving from the hertzian deformation of the contacts among particles and another that takes into account the linear elastic deformation of the powder skeleton. A simple model based in a one pore unit cell is presented to support the mathematical model.
Authors: Enrico Armentani, G.F. Bocchini, G. Cricrì, Renato Esposito
Abstract: The deformation under radial pressure of rectangular dies for metal powder compaction has been investigated by FEM. The explored variables have been: aspect ratio of die profile, ratio between diagonal of the profile and die height, insert and ring thickness, radius at die corners, interference, different insert materials, i. e. conventional HSS, HSS from powders, cemented carbide (10% Co). The analyses has ascertained the unwanted appearance of tensile normal stress on brittle materials, also “at rest”, and even some dramatic changes of stress patterns as the die height increases with respect to the rectangular profile dimensions. Different materials behave differently, mainly due to difference of thermal expansion coefficients. Profile changes occur when the dies are heated up to the temperature required for warm compaction. The deformation patterns depend on compaction temperature and on thermal expansion coefficients.
Authors: Z. Jiang, C. Lucien Falticeanu, I.T.H. Chang
Abstract: With the onging trend of reducing the weight of automotive parts, there is also an increasing trend in the use of light alloys. Recently, aluminum powder metallurgy has been the subject of great attention due to the combination of the lightweight characteristics of aluminium and the efficient material utilisation of the powder metallurgical process, which offer attractive benefits to potential end-users. Conventional press and sinter route of non-ferrous P/M products are based compaction at room temperature prior to the sintering cycle. However, warm compaction process has successfully provided increased density in ferrous powder metallurgy parts, which contributes to better mechanical properties and consequently overall performance of those parts. This study is aimed at exploring the use of warm compaction process to aluminium powder metallurgy. This paper presents a detailed study of the effect of warm compression and sintering conditions on the resultant microstructures and mechanical properties of Al-Cu-Mg-Si PM blend.
Authors: Te Su Kwak
Abstract: This study is focused on the manufacturing technique of powder injection molding of watch case made from zirconia powder. A series of computer simulation processes were applied to the prediction of the flow pattern in the inside of the mould and defects as weld-line. The material properties of melted feedstock, including the PVT graph and thermal viscosity flowage properties were measured to obtain the input data to be used in a computer simulation. Also, a molding experiment was conducted and the results of the experiment showed a good agreement with the simulation results for flow pattern and weld line location. On the other hand, gravity and inertia effects have an influence on the velocity of the melt front because of the high density of ceramic powder particles during powder injection molding in comparison with polymer’s injection molding process. In the experiment, the position of the melt front was compared with the upper gate and lower gate positions. The gravity and inertia effect could be confirmed in the experimental results.
Authors: Chul Jin Hwang, Y.B. Ko, Hyung Pil Park, S.T. Chung, Byung Ohk Rhee
Abstract: Powder Injection Molding (PIM) has recently been recognized as an advanced manufacturing technology for low-cost mass production of metal or ceramic parts of complicated geometry. With this regards, design technology of dental scaler tip PIM mold, which has complex shape and a slim core pin of 0.6 mm diameter, with the help of computer-aided analysis for powder injection molding process was developed. Computer-aided analysis for dental scaler tip mold was implemented by finite element method with non-Newtonian fluid, modified Cross model viscosity, PvT data of powder/binder mixture. The core deflection analysis of dental scaler tip PIM mold during PIM filling process was also investigated. Compter-aided analysis results, such as filling pattern, weldline formation, and air vent position prediction were investigated and eventually showed good agreements with experimental results.
Authors: Chul Jin Hwang, Y.B. Ko, Hyung Pil Park, S.T. Chung, Byung Ohk Rhee
Abstract: With the capability of net shaping for complex 3D geometry, powder injection molding (PIM) is widely used for automotive parts, electronics and medical industry. In this study, an ultrasonic dental scaler tip produced by machining process was redesigned for the PIM process. An injection mold was designed and machined to produce the dental scaler tip by the PIM process. The mold design was aided by CAE analysis. A PIM feedstock was made of SUS316L powder and a wax based binder. The filling balance in the mold was checked by a short shot test with LDPE and the PIM feedstock. Production capability of the PIM process for the dental scaler tip was examined with the mold. Although there were minor problems such as a discoloration around the gate and a flashing at the air vent, the PIM process turned out to be an excellent substitute for machining process to manufacture the ultrasonic dental scaler tip.
Authors: Eung Ryul Baek, Sugen Supriadi, Chul Jin Choi, Byong Taek Lee, Jae Wook Lee
Abstract: Micro powder metal injection molding has received attention as a manufacturing technology for microparts. Small powder size is very useful in achieving detailed structures. STS nanopowders with an average diameter of 100 nm and STS micropowders with an average diameter of 5 micron were utilized to produce feedstock. The mixing behavior of the feedstock was indicated that the nanoparticle feedstock produce highest mixing torque at various powder_loading than the micropowder feedstock. Ares rheometer was utilized to examine visco-elatic flow behavior. The nanoparticles feedstocks showed that elastic properties are dominant in flow behavior and high viscosity. Whereas the micropowders feedstocks, viscous properties are dominant in flow behavior and less viscosity.
Authors: Gemma Herranz, B. Levenfeld, A. Várez
Abstract: In this present investigation, Metal Injection Moulding (MIM) of M2 High Speed Steel (HSS) parts using a wax-High Density Polyethylene (HDPE) binder is shown. This work is focused on the examination of the sintering densification and microstructure evolution of the parts. The injection molding process of the feedstock has been optimized to obtain high quality green parts. The elimination of organic binder was carried out by thermal debinding under inert atmosphere. In order to keep carbon in the sample that could improve the sintering process, incomplete debinding was performed between 450 and 600 °C. The specimens were sintered at temperatures between 1210 and 1280oC in high vacuum atmosphere, obtaining the 98% of the theoretical density. A homogeneous distribution of fine M6C carbides was obtained as well as V-rich carbides (MX) during sintering which reinforced the HSS and hence increasing the mechanical properties of the parts. In the samples with higher residual carbon content, the sintering window was extended up to 20 degrees and the optimum temperature was lower.

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