A quantitative characterisation of porosity in a Cr–Mo sintered steel using image analysis

Cipolloni, Giulia; Menapace, C.; Cristofolini, I.; Molinari, A.

doi:10.1016/j.matchar.2014.05.005

Cited by 11 publications

(7 citation statements)

References 6 publications

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“…Figure 4 provides pore size and pore shape distribution values of 0.5Cr alloy. It is seen from Figure 4(a) that the 0.5Cr alloy consists mainly of the pores below 5 μm 2 in area, which is much smaller than that of the low density alloys (30–60 μm 2 ) [16]. Pore shape was characterised using a shape factor f circle [17] where A is the area of the pore and P is the circumference of the pore in the measurement plane.…”

Section: Resultsmentioning

confidence: 99%

Dynamic properties of high-density low-alloy PM steels

et al. 2017

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PM steels with density higher than 7.5 g cm −3 were prepared from binder-treated powder, and the effects of alloying elements and microstructure on dynamic performance were studied. Although the addition of 1.5 wt-% Cu improves the tensile strength, it impairs toughness of the alloy by the formation of low-toughness pearlite. The 0.5 wt-% Cr addition promotes the formation of Ni-rich martensite and bainite at the expense of pearlite, which is beneficial to strengthen and homogenise the microstructure. The 0.5Cr alloy exhibits improved tensile strength and fatigue strength without sacrificing impact toughness, which exhibits high potential to be used for dynamic and cyclic loading applications. The tensile strength and fatigue endurance strength under 10 7 cycles of 0.5Cr alloy achieve 1350 and 562 MPa respectively, and impact energy is as high as 21.1 J. The enhanced fatigue life is attributed to the high density, smaller pore size, rounder pores and composite-like microstructure.

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Section: Resultsmentioning

confidence: 99%

Dynamic properties of high-density low-alloy PM steels

et al. 2017

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“…The structure of pore has significant effect on the mechanical and fatigue properties for C/C composites. The number, size, morphology, and distribution are considerable factors when characterizing microstructure of pores (Cipolloni, Menapace, Cristofolini, & Molinari, ). Therefore, the parameters of Area

A

, equivalent diameter

D_{e q}

, and shape coefficient

f_{c i r c l e}

are selected, and their distributions are calculated and statistical analyzed.…”

Section: Resultsmentioning

confidence: 99%

Section: Characterization Of Porementioning

confidence: 99%

Quantitative characterization of the carbon/carbon composites components based on video of polarized light microscope

Song

et al. 2017

Microscopy Res & Technique

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The components of carbon/carbon (C/C) composites have significant influence on the thermal and mechanical properties, so a quantitative characterization of component is necessary to study the microstructure of C/C composites, and further to improve the macroscopic properties of C/C composites. Considering the extinction crosses of the pyrocarbon matrix have significant moving features, the polarized light microscope (PLM) video is used to characterize C/C composites quantitatively because it contains sufficiently dynamic and structure information. Then the optical flow method is introduced to compute the optical flow field between the adjacent frames, and segment the components of C/C composites from PLM image by image processing. Meanwhile the matrix with different textures is re-segmented by the length difference of motion vectors, and then the component fraction of each component and extinction angle of pyrocarbon matrix are calculated directly. Finally, the C/C composites are successfully characterized from three aspects of carbon fiber, pyrocarbon, and pores by a series of image processing operators based on PLM video, and the errors of component fractions are less than 15%.

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“…When it comes to gears for heavy-duty and automotive transmissions, fatigue properties play a vital role and density has a significant effect on the final performance of the gear since it has a direct relation to the mechanical properties. Porosity plays a significant influence on the properties of PM steel [8] and the pore size, pore structure and its distribution within the sample are known to affect the fatigue properties [9][10][11] by initiating the crack.…”

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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A quantitative characterisation of porosity in a Cr–Mo sintered steel using image analysis

Cited by 11 publications

References 6 publications

Dynamic properties of high-density low-alloy PM steels

Dynamic properties of high-density low-alloy PM steels

Quantitative characterization of the carbon/carbon composites components based on video of polarized light microscope

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

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