Defining the pores in PM components

Dlapka, M.; Danninger, Herbert; Gierl, Christian; Lindqvist, Björn H.

doi:10.1016/s0026-0657(10)70093-x

Cited by 45 publications

(51 citation statements)

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“…Total and open porosity were measured through the Archimedes' method according to standard ASTM B311. For a deeper analysis of the permeability of the pore network during carburization the He pycnometry is preferable [27], however, this paper is more focused on the role of the pore network in dictating the fatigue crack propagation. For this reason, these measurements were complemented by image analysis of micrographs taken by optical microscopy, in order to investigate the morphology and spatial distribution of the pores located at the tooth root, inside the tooth and in the gear body.…”

Section: Parameter Valuementioning

confidence: 99%

Tooth Root Bending Fatigue Strength of High-Density Sintered Small-Module Spur Gears: The Effect of Porosity and Microstructure

Fontanari

Molinari

Marini

et al. 2019

Metals

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The present paper is aimed at investigating the effect of porosity and microstructure on tooth root bending fatigue of small-module spur gears produced by powder metallurgy (P/M). Specifically, three steel variants differing in powder composition and alloying route were subjected either to case-hardening or sinter-hardening. The obtained results were interpreted in light of microstructural and fractographic inspections. On the basis of the Murakami a r e a method, it was found that fatigue strength is mainly dictated by the largest near-surface defect and by the hardness of the softest microstructural constituent. Owing to the very complicated shape of the critical pore, it was found that its maximum Feret diameter is the geometrical parameter that best captures the detrimental effect on fatigue.

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Section: Parameter Valuementioning

confidence: 99%

Tooth Root Bending Fatigue Strength of High-Density Sintered Small-Module Spur Gears: The Effect of Porosity and Microstructure

Fontanari

Molinari

Marini

et al. 2019

Metals

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“…In order to perform capsulefree HIP, it is necessary to have the surface open pores closed; otherwise, any presence of surface open pores which are interconnected will not be densified after capsule-free HIP [17,18] whereas closed pores are successfully HIP:ed to reach full density [19,20]. When it comes to water-atomised low-alloyed steel powder, it has been shown that the transition from open to closed porosity occurs around 95% of the density levels after sintering at high temperatures [21] which enables the surface pore closure [16]. Also, reaching such high density is necessary for PM steel components to retain the dimensional stability after HIP.…”

Section: Introductionmentioning

confidence: 99%

Experimental and finite element simulation study of capsule-free hot isostatic pressing of sintered gears

Sundaram

Khodaee

Andersson

et al. 2018

Int J Adv Manuf Technol

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A novel approach to reach full density in powder metallurgy (PM) components is demonstrated in this work. Water-atomised Moprealloyed steel powder is utilised for manufacturing cylindrical and gear samples through double pressing and double sintering (DPDS) process route. The effect of sample geometry and powder size fraction on densification is investigated and it is found that the DPDS route enables a density level of > 95% which is sufficient to eliminate the surface open pores. Reaching such high density is necessary, in order to perform capsule-free hot isostatic pressing (HIP). After HIP, full densification is achieved for the cylindrical samples and only near full density is realised for the gears resulting in neutral zone formation due to the density gradient. In order to predict the densification behaviour during the compaction, FEM simulations considering the gear geometry are performed for both the pressing stages and HIP. The simulation predicted a similar densification behaviour with the formation of the neutral zone. The proposed DPDS route with capsule-free HIP in combination with FEM simulation is demonstrated as a potential route for manufacturing full-density PM steel components, e.g. gears, suitable for high-performance applications.

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“…The presence of porosity, playing a very important role with great influence on properties [1][2][3][4][5], represents a real issue in PM parts.…”

Section: Introductionmentioning

confidence: 99%

“…The most frequently used definition is the total porosity, which is the total volume fraction of empty space in the specimen [2]. This parameter is usually measured using water displacement methods.…”

Section: Introductionmentioning

confidence: 99%

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Microdeformation Processes in Soft Magnetic Compounds

et al. 2017

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Porosity can be defined in different ways. The most frequently used definition is the total porosity, which is the total volume fraction of empty space in the specimen. The presence of pores strongly affects the fracture mode. Besides the evaluation of geometry and quality of connections, fractographic analysis enables a quantification of the important microstructural characteristics of the plane porosity. This quantity allows to quantify the existing relations between microstructure and properties. The fractographic evaluation of the distribution of microdeformation processes in the volume of experimental material demonstrates the influence of porosity on the concentration of deformation flows into the microvolume of connections. Plain porosity contributes to the recognition of critical microstructural defects and therefore, to enable evaluating the relationship between the processing parameters, microstructural constituents, and pores. In the fractography evaluation, the analysis of the quality of interparticle bonding using determination of elementary types of fracture facets allows to interpret the mechanical and plastic properties of investigated materials.

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Defining the pores in PM components

Cited by 45 publications

References 1 publication

Tooth Root Bending Fatigue Strength of High-Density Sintered Small-Module Spur Gears: The Effect of Porosity and Microstructure

Tooth Root Bending Fatigue Strength of High-Density Sintered Small-Module Spur Gears: The Effect of Porosity and Microstructure

Experimental and finite element simulation study of capsule-free hot isostatic pressing of sintered gears

Microdeformation Processes in Soft Magnetic Compounds

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