Study of high temperature wetting and infiltration for optimising liquid phase sintering in low alloy steels

Oro, Raquel; Campos, Mónica; Torralba, J. M.

doi:10.1179/1743290111y.0000000007

Cited by 29 publications

(32 citation statements)

References 31 publications

(62 reference statements)

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“…channels in the surrounding of the master alloy particles [22,32], favoring the formation of a micro-climate inside the secondary pore left by the master alloy particle. The liquid master alloy continuously changes its composition due to the diffusion of alloying elements and the dissolution of the iron base particles.…”

Section: Model For Microstructure Development and The Oxide Distributmentioning

confidence: 99%

Effect of processing conditions on microstructural features in Mn–Si sintered steels

Oro¹,

Hryha²,

Campos³

et al. 2014

Materials Characterization

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• Oxide distribution in steels containing oxidation-sensitive elements• Mn, Si introduced in a master alloy powder, mixed with a base iron powder• Selective oxidation of Mn and Si on iron grain boundaries Sintering of steels containing oxidation sensitive elements is possible if such elements are alloyed with others which present lower affinity for oxygen. In this work, a master alloy powder containing Fe-Mn-Si-C, specifically designed to create a liquid phase during sintering, has been used for such purpose. The effect of processing conditions such as sintering temperature and atmosphere was studied with the aim of describing the microstructural evolution as well as the morphology and distribution of oxides in the sintered material, evaluating the potential detrimental effect of such oxides on mechanical properties.Chemical analyses, metallography and fractography studies combined with X-ray photoelectron spectroscopy analyses on the fracture surfaces were used to reveal the main mechanism of fracture and their correlation with the chemical composition of the different fracture surfaces.The results indicate that the main mechanism of failure in these steels is brittle fracture in the surrounding of the original master alloy particles due to degradation of grain boundaries by the presence of oxide inclusions. Mn-Si oxide inclusions were observed on intergranular decohesive facets. The use of reducing atmospheres and high sintering temperatures reduces the amount and size of such oxide inclusions. Besides, high heating and cooling rates reduce significantly the final oxygen content in the sintered material. A model for microstructure development and oxide evolution during different stages of sintering is proposed, considering the fact that when the master alloy melts, the liquid formed can dissolve some of the oxides as well as the surface of the surrounding iron base particles.

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Section: Model For Microstructure Development and The Oxide Distributmentioning

confidence: 99%

Effect of processing conditions on microstructural features in Mn–Si sintered steels

Oro¹,

Hryha²,

Campos³

et al. 2014

Materials Characterization

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“…Figure A represents the evolution of the contact angle during the wetting experiments, while Figure B and C corresponds to the liquid‐solid interface on Fe and Fe‐C substrates, respectively. Due to the absence of a specific melting point, the progressive melting of the alloy within a temperature range makes the wetting calculations even more complicated, since it is not easy to separate the first stages of spreading from the melting process itself …”

Section: Resultsmentioning

confidence: 99%

Novel multiuse liquid phase promoter for PM components

2019

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The aim of this work was to characterize the behavior of a novel multiuse B‐free alloy that was designed as a liquid phase promoter and as a filler material for sintering and brazing steels in N2‐H2. Through thermodynamic calculations, a new Cu‐Fe‐Ni‐Si alloy (named LP) has been designed showing a proper melting point suitable for being used at temperatures below 1100°C, with good wetting behavior that allows it use as brazing material and liquid phase former. This new boron‐free alloy has shown good dimensional behavior, good brazeability, and competitive mechanical properties. These demonstrated features allow the developed alloy it use as braze material for PM parts in industrial furnaces as well as master alloy to promote transient liquid phase in PM structural steels.

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“…The wettability of the master alloy Fe-Mn-Si-C on plain iron substrates under N 2 -10H 2 atmosphere was reported in previous studies and compared with the wettability of Cu on the same type of substrates but under Ar atmosphere 15,16 . In those studies, the wetting angle provided by the master alloy was reported to be around 20º, while that of Cu was approximately 70º.…”

Section: Bwetting Experimentsmentioning

confidence: 99%

“…This evolution of the wetting angle is due to the dissolution of the iron oxide layer by the liquid master alloy. The ability of this master alloy to dissolve the iron substrate is due to the chemical compatibility between the iron substrate and the liquid formed 16 . The conditions used for the wetting experiments performed represent the worst case scenario where no reducing agents are available.…”

Section: Bwetting Experimentsmentioning

confidence: 99%

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Lean alloys in PM: from design to sintering performance

et al. 2012

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Low alloy sintered steels with an optimized content of alloying elements require the use of promising candidates such as Mn and Si which can provide improved properties with minimum contents at a lower and less volatile price. The introduction of these alloying elements in the form of a master alloy powder prevents, to some extent, the oxidation and allows a proper "tailoring" of its composition to accomplish particular goals. In this sense, low melting point alloys are especially interesting since they provide the formation of a liquid phase which enhances sintering and promotes the homogeneous distribution of the alloying elements within the compact. In this work, the "product developing" process of master alloys containing Fe-Mn-Si is described, from the theoretical design to the sintering performance. Low melting point compositions were calculated by using ThermoCalc® software and successively manufactured by gas atomization. Liquid phase features are described in terms of melting temperatures and wetting behavior. The effects of the liquid phase (produced by the added master alloys) are studied by differential thermal analysis and dilatometry. Besides, to depict the behavior of liquid phase during heating, interrupted sintering experiments under high cooling rates were carried out, and the results have been discussed through the microstructure examination.

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Study of high temperature wetting and infiltration for optimising liquid phase sintering in low alloy steels

Cited by 29 publications

References 31 publications

Effect of processing conditions on microstructural features in Mn–Si sintered steels

Effect of processing conditions on microstructural features in Mn–Si sintered steels

Novel multiuse liquid phase promoter for PM components

Lean alloys in PM: from design to sintering performance

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