The effect of anisotropic dimensional change on the precision of steel parts produced by powder metallurgy

Cristofolini, I.; Menapace, C.; Cazzolli, Marco; Rao, A.C. Umamaheshwer; Pahl, W.; Molinari, A.

doi:10.1016/j.jmatprotec.2012.02.009

Cited by 25 publications

(23 citation statements)

References 8 publications

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“…These phenomena are more pronounced in the longitudinal specimen than in the transversal specimen, whereas the slope of the curves relevant to the two specimens above the alpha/gamma transformation and during the isothermal holding is rather similar. These results confirm what was observed in the previous works: shrinkage starts at low temperatures with a significant anisotropy in the ferritic region, and particularly below the Curie point; in the austenitic region, both during heating and the isothermal holding, anisotropy of dimensional change is much less pronounced.…”

Section: Resultssupporting

confidence: 92%

“…Sintering shrinkage of uniaxially cold compacted iron and iron alloys is anisotropic. The most common behavior results in a larger shrinkage along the compaction direction than in the compaction plane, and the presence of a liquid phase by Cu and P addition reduces shrinkage anisotropy . In swelling systems, expansion in the compaction plane is larger than that along the compaction direction …”

Section: Introductionmentioning

confidence: 99%

“…In case of a cold isostatically pressed iron green compact, dilatometry curves of specimens cut along different directions do not show significant differences, confirming the expected isotropic shrinkage. 14,15 Conversely, a noticeable difference is displayed by the curves of uniaxially cold compacted iron alloys, particularly in the early stage of sintering in the alpha field below the Curie transformation 1,16,17 : the longitudinal specimen starts shrinking at a lower temperature than the transversal specimen. The same behavior was observed in Cr-Mo low-alloy steel at higher temperatures in the austenitic region.…”

Section: Introductionmentioning

confidence: 99%

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The Anisotropy of Dimensional Change on Sintering of Iron

et al. 2015

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H€ ogan€ as AB, SE-263 83 H€ ogan€ as, SwedenThe anisotropy of dimensional change on the sintering of iron was investigated by dilatometry. Dimensional changes are different along the longitudinal and transversal directions, and shrinkage is more pronounced parallel to the compaction direction. This phenomenon is particularly pronounced during the early stage of sintering, in the alpha field below the Curie temperature. The results were elaborated according to the kinetics model for shrinkage to calculate an effective diffusion coefficient along the two directions. Such an effective diffusion coefficient is higher parallel to the compaction direction than perpendicular to it, and both are larger than the diffusion coefficient calculated on the basis of the activation energy reported in the literature for pure iron. This discrepancy is attributed to the defectiveness introduced by cold compaction in the particle contact regions, which may enhance diffusivity owing to the dislocation pipe mechanism, which, in turn, is particularly intense below the Curie temperature. This interpretation may also justify anisotropy of shrinkage because the powder particles are inhomogeneously deformed by uniaxial cold compaction. The enhanced diffusion coefficient increases with time and shows a maximum at temperatures below the Curie point. This trend was discussed with reference to the self-activated sintering mechanism.

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Section: Resultssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Anisotropy of Dimensional Change on Sintering of Iron

et al. 2015

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“…It is also interesting to highlight that the highest density is obtained by the samples sintered at slow rate, i.e., 5ºC. Slow sintering rate caused the powder particles to form perfect necking among them which is manifested by smaller swelling [8] hence density did not drop much, i.e., less volumetric expansion (figure 2).…”

Section: Resultsmentioning

confidence: 99%

Effects of forming temperature and sintering rate to the final properties of FeCuAl powder compacts formed through uniaxial die compaction process

Rahman¹,

Ismail

Sopyan

et al. 2018

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. This paper presents the outcomes of an experimental investigation on the effects of forming temperature and sintering schedule to the final characteristics of FeCuAl powder mass formed at different temperature and sintered at different schedule. A lab-scale uni-axial die compaction rig was designed and fabricated which enabled the compaction of powder mass at room temperature as well as elevated temperature. Iron (Fe) powder ASC 100.29 was mechanically mixed with other elemental powders, namely copper (Cu), and aluminum (Al) for 60 minutes and compacted at three different temperature, i.e., 30°C, 150°C, and 200°C by applying 425 MPa of simultaneous downward and upward axial loading to generate green compacts. The as-pressed samples were inspected visually and the defect-free green compacts were subsequently sintered in an argon gas fired furnace at 800°C for 60 min at three different heating/cooling rates, i.e., 5, 10, and 15°C/min, respectively. The sintered samples were then characterised for their physical, electrical, and mechanical properties. The microstructures of the sintered samples were also analysed. The results revealed that a forming temperature of 150°C and a sintering rate of 10°C/min could produce a product with better characteristics. IntroductionPure materials are proven to have a lot of disadvantages, i.e., soft, brittle, easy to degrade in hot and humid environment, etc. In order to overcome the disadvantages of pure materials, other materials are used as additives to produce a coherent mass named as alloy which is a homogeneous mixture of two or more materials where the dominant one is called matrix and the other materials are dissolved within it. Alloys have superior properties compared to individual pure materials [1][2]. Alloys are produced either through casting process or mechanical alloying. Casting process requires huge amount of thermal energy to melt the metals and subsequently machining operation to produce end products. On the other hand, mechanical alloying is used to prepare a solid solution of more than one metallic or non-metallic materials and subsequently the solid solution is pressed and sintered to produce end products. The solid solution is prepared through high energy ball milling of the intended powders for a long time. Both methods, i.e., casting and mechanical alloying are found to be time consuming and energy ineffective.

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“…They tested the machinability of the iron-based PM steels. Cristofolini et al [4] produced ring-shaped parts with a Fe-Cu-P alloy by a conventional powder metallurgy process. They investigated the effect of anisotropic dimensional change on the precision of PM parts.…”

Section: Introductionmentioning

confidence: 99%

Thermal Analyses for Induction Sintering of Powder Metal Compacts up to Sintering Temperature

Çavdar¹,

Atík²,

Akgül³

et al. 2016

Metallofiz. Noveishie Tekhnol.

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Induction sintering is developed as an alternative method to conventional sintering in order to sinter iron-based powder metal (PM) compacts. In this study, the 12 kW power and 30 kHz frequency induction-sintering machine is used for 3 wt.% copper-mixed iron. The effects of different shapes and sizes of the induction coil, and temperature differences on the PM compacts up to sintering temperature are investigated; these parameters are determined both theoretically and experimentally during induction sintering. Iron-based PM compacts are sintered at 1120C. Induction sintering of iron-based PM compacts are simulated using a program to examine the effects of magnetic flux and temperature distribution in the sample over time. The results are compared with the experimental studies.Індукційне спікання було розроблено як альтернатива звичайному спі-канню, щоб спікати брикети порошкових матеріялів (ПМ) на основі залі-за. В даній роботі використано індукційну аґломераційну машину поту-жністю у 12 кВт і частотою у 30кГц для спікання суміші заліза з 3 ваг.% міді. Досліджено впливи різних форм і розмірів індукційної шпулі, ріж-ниць температур на брикети ПМ аж до температури спікання; ті парамет-ри було досліджено як теоретично, так й експериментально під час індук-ційного спікання. Брикети ПМ на основі заліза спікалися при 1120C. Ін-дукційне спікання брикетів ПМ на основі заліза також модельовано з ви-користанням програми, яка досліджує впливи магнетного потоку та роз-поділу температури у зразку з часом. Результати порівняно з результата-ми експериментальних досліджень. Индукционное спекание было разработано как альтернатива обычному спеканию, чтобы спекать прессовки порошковых материалов (ПМ) на ос-нове железа. В данной работе использована индукционная агломерацион-ная машина мощностью 12 кВт и частотой 30 кГц для спекания смеси же-леза с 3 масс.% меди. Исследованы влияния различных форм и размеров индукционных катушек, разниц температур на брикеты ПМ вплоть до температуры спекания; эти параметры были исследованы как теоретиче-ски, так и экспериментально во время индукционного спекания. Брикеты ПМ на основе железа спекались при 1120C. Индукционное спекание брикетов ПМ на основе железа также смоделировано с использованием программы, которая исследует влияние магнитного потока и распределе-ния температуры в образце со временем. Результаты сопоставлены с ре-зультатами экспериментальных исследований.

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The effect of anisotropic dimensional change on the precision of steel parts produced by powder metallurgy

Cited by 25 publications

References 8 publications

The Anisotropy of Dimensional Change on Sintering of Iron

The Anisotropy of Dimensional Change on Sintering of Iron

Effects of forming temperature and sintering rate to the final properties of FeCuAl powder compacts formed through uniaxial die compaction process

Thermal Analyses for Induction Sintering of Powder Metal Compacts up to Sintering Temperature

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