Silicon microsegregation and first stage graphitization in white cast irons

Swindells, N.; Burke, Jan

doi:10.1007/bf02811605

Cited by 13 publications

(17 citation statements)

References 5 publications

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“…It is well known that silicon promotes graphitizing of white-solidified cast irons and steels upon annealing above or slightly below A C1 [11,24,25,[40][41][42]. In the present study, graphitizing is observed at much lower temperatures and comparably short annealing times.…”

Section: Thermal Stability Of the Eutectic Cementitecoarsening And Grsupporting

confidence: 54%

“…These are the high silicon content, which is inherited from the cast iron substrate, and the high degree of microstructural refinement due to the rapid solidification of the remolten layer. Both a high silicon content and a high volume density of interfaces related to a refined microstructure can promote graphitizing upon annealing above the eutectoid temperature Ac 1 (�727°C) [24,25].…”

Section: Introductionmentioning

confidence: 99%

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Low‐temperature annealing and graphitizing of white‐solidified low‐alloy cast irons

Kante

Leineweber

Holst

et al. 2019

Materialwissenschaft Werkst

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Hypoeutectic iron‐carbon and iron‐carbon‐silicon model alloys as well as conventional cast irons GJL‐250mod and EN‐GJS‐600‐3 have been produced and processed by different solidification techniques, i. e. mold casting, electron beam surface remelting and melt spinning. The white‐solidified alloys exhibit different degrees of microstructural refinement indicated by a secondary dendrite arm spacing of 0.3 μm–12 μm. The effects of microstructural refinement and silicon content on the hardness as well as on coarsening of cementite and graphitizing at temperatures of 540 °C to 670 °C have been investigated. The hardness of the as‐solidified alloys increases with decreasing secondary dendrite arm spacing and increasing silicon content. High silicon content effectively retards coarsening of pearlitic cementite, and thus is beneficial to retain the hardness at small thermal load. On the downside, high degree of microstructural refinement and high silicon content promote and accelerate graphitizing at temperatures > 600 °C. The results are discussed in terms of the applicability of a recently developed two‐step surface treatment for cast irons, i. e. electron beam remelting followed by nitriding.

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Section: Thermal Stability Of the Eutectic Cementitecoarsening And Grsupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Low‐temperature annealing and graphitizing of white‐solidified low‐alloy cast irons

Kante

Leineweber

Holst

et al. 2019

Materialwissenschaft Werkst

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“…The change in the sign of the slope of the path followed by the austenite composition is thus related to the onset of the eutectic reaction. Interestingly enough, the predicted increase of the composition of the proeutectic austenite during cooling may explain the apparent positive segregation of silicon previously reported [2,11] in the case of high volume fraction of proeutectic (or offeutectic) austenite. Experimental as well as calculated data may be arranged to plot cumulative distribution of silicon and manganese in austenite.…”

Section: A Solidification In the Stable System (Samples A-1 Andmentioning

confidence: 74%

“…been reported, [2,11] which could not be clearly understood. Also, Charbonnier and Margerie [2] observed that segregation CHEMICAL heterogeneities, which build up during is slightly less marked in as-cast malleable irons, but Feest solidification of cast irons at the scale of the solidification et al [12] found high positive segregation of silicon in white microstructure (microsegregations), have been investigated cast iron.…”

Section: Introductionmentioning

confidence: 89%

“…In this line of studies, this work presents an attempt for a long time because of their influence on the properties to describe the complex relationship between the developof cast products. [1][2][3][4][5][6][7][8][9][10][11] Microsegregations affect the microment of the solidification microstructures and buildup of structure resulting from the solidification step, namely, the microsegregation in spheroidal graphite (SG) cast irons by gray (stable) to white (metastable) eutectic transition, but coupling an experimental investigation and a modeling also the solid-state transformations during cooling or heat approach. treatments.…”

Section: Introductionmentioning

confidence: 99%

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Study of microsegregation buildup during solidification of spheroidal graphite cast iron

Selig¹,

Lacaze

2000

Metall Mater Trans B

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This work presents an attempt to describe the complex relationship between the development of the solidification microstructures and buildup of microsegregation in spheroidal graphite (SG) cast irons by coupling an experimental investigation and a modeling approach. Experimental characterization of microsegregation in cast iron was made by means of point counting microanalysis along a grid. With this method, the differences of silicon distribution in alloys solidified in the stable system, the metastable system, or in both systems were clearly evidenced. The distribution of manganese in alloy solidified in the stable system was also investigated. It has been, in particular, observed that alloys solidified in the stable (respectively, metastable) system present significant negative (respectively, positive) segregation of silicon, and that alloys solidified in both systems are much less segregated. The solidification path of these alloys has been conveniently reproduced by means of predictions made with a physical model accounting for the nature of the alloy, either hypoeutectic or hypereutectic, and for the sensitivity to temperature and composition of the partition coefficient of alloying elements.

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Nitriding of White‐Solidified Fe–C–Si Alloys: Diffusion Path Concept Applied to Inhomogeneous Microstructures

2021

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Gray-solidified cast irons are frequently used to manufacture machine and engine parts due to their low cost, good compressive strength, and high damping capacity. [1,2] Their use is, however, often limited by poor surface hardness and corrosion resistance. Both can be notably improved by a duplex surface treatment developed in recent years. [3][4][5][6] First, the surface of the cast iron is remelted, e.g., by an electron beam or plasma arc. This produces a white-solidified, ledeburitic [7,8] surface layer, which is hard and abrasion-resistant. Afterward, the material is nitrided to enhance the corrosion resistance by the formation of a dense surface layer composed of the main Fe (carbo)nitrides, γ 0 -Fe 4 (N,C) and ε-Fe 3 (N,C) 1þx (Table 1), denoted compound layer. Note that nitriding without remelting leads to less favorable microstructures because coarse graphite particles contained in gray-solidified cast irons are detrimental to the compound layer formation. [3,4,[9][10][11] Although the general advantages of the previously described duplex treatment have been demonstrated, the nitriding behavior of the white-solidified surface layers turns out to be complex and incompletely understood. [12][13][14][15][16][17][18][19] The research of the current authors [12,18,19] aims at elucidating the complex nitriding behavior of the remelted surface layers by controlled gas nitriding of white-solidified Fe-3.5 wt% C-0/1.5/3 wt% Si alloys, serving as model alloys for commercially available ferritic cast iron grades subjected to remelting and nitriding. Note that, in contrast to ferritic cast irons, pearlitic cast irons often contain non-negligible additions of Mn and Cu, which may additionally affect the nitriding behavior. [17] The microstructure of white-solidified Fe-3.5 wt% C-1.5/3 wt% Si alloys, having C and Si contents typical of cast irons, is mainly composed of coarse eutectic cementite plates, θ-Fe 3 C 1Àz (Table 1), embedded in ferrite and pearlite. [20,21] The latter result from the decomposition of primary and eutectic γ-Fe during cooling after solidification. In addition, a minor volume fraction of Fe 23 Si 5 C 4 -type silicocarbide (Table 1) is contained in the alloys. [22][23][24] The distribution of Si in the white-solidified microstructure is very heterogeneous. The Si/Fe atomic ratio in the eutectic and pearlitic θ is u Si,θ < 3 Â 10 À4 and, here, considered negligible, say u Si,θ ! 0. [12] The Si/Fe atomic ratio in Fe 23 Si 5 C 4 is u Si,Fe 23 Si 5 C 4 % 0.22; however, it might take also values slightly different from 0.22 due to a possibly mixed Fe/Si site [23,24] and extended lattice defects affecting the composition. [22] The Si content in α-Fe relates to the Si content of γ-Fe, which is affected by Si segregation during solidification. The Si content in the center of γ-Fe dendrites is typically similar to the Si content of the alloy, while the outer rim of dendrites and last-to-freeze regions are enriched in Si. [25] The Si content in eutectic γ-Fe is higher

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Silicon microsegregation and first stage graphitization in white cast irons

Cited by 13 publications

References 5 publications

Low‐temperature annealing and graphitizing of white‐solidified low‐alloy cast irons

Low‐temperature annealing and graphitizing of white‐solidified low‐alloy cast irons

Study of microsegregation buildup during solidification of spheroidal graphite cast iron

Nitriding of White‐Solidified Fe–C–Si Alloys: Diffusion Path Concept Applied to Inhomogeneous Microstructures

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