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1

Modification of macrostructure of nickel superalloys with cobalt nanoparticles

Binczyk F., Śleziona J., Gradoń P.

Kompozyty

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2011

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R. 11, nr 1

49-54

EN

The paper presents the results of studies on the effect of combined surface and bulk modifications on the macrostructure of castings made from remelted, post-production IN-713C, IN-100 and MAR-247 waste alloys. Surface modification was carried out by applying onto the wax pattern surface, a coating containing zirconium silicate and cobalt aluminate. Bulk modification was carried out when the cast liquid alloy was passed through a special ceramic filter containing, among others, cobalt aluminate. The nanoparticles of cobalt, acting as crystallisation nuclei, are the product of a modifier reaction (CoAl2O4 inoculant) with the chemically active constituents of the nickel alloys and with the additional filter components in the form of Al and Ti powders. The filters were placed in the mould pouring basin. The beneficial effect of combined modification on the macrostructure (equiaxial crystals) and mechanical properties was stated. The effect of the active constituents present in the nickel alloys and in the filter material was confirmed. A particularly strong refining effect on the macrostructure of equiaxial crystals was obtained in the MAR-247 alloy, which contained the strongest chemically active additives of Hf, Ta and Nb. A hypothetical model of the surface and bulk modification was developed. A strong influence of the alloy pouring temperature on the modification effect was reported. Modification was most effective when the pouring temperature did not exceed 1440°C.

PL

Zamieszczono wyniki badań wpływu łącznego modyfikowania powierzchniowego i objętościowego na makrostrukturę odlewów wykonanych po przetopie odpadów poprodukcyjnych ze stopów IN-713C, IN-100 i MAR-247. Modyfikację powierzchniową zrealizowano poprzez naniesienie na model woskowy powłoki zawierającej krzemian cyrkonu i glinian kobaltu. Modyfikację objętościową zrealizowano podczas odlewania ciekłego stopu przez specjalne filtry ceramiczne, zawierające między innymi glinian kobaltu. Nanocząstki kobaltu, pełniące rolę zarodków krystalizacji, są produktem reakcji modyfikatora (inoculant CoAl2O4) z aktywnymi chemicznie składnikami stopów niklu oraz dodatkowymi składnikami filtrów w postaci proszków Al i Ti. Filtry umieszczono w zbiorniku wlewowym formy. Stwierdzono korzystny wpływ łączonej modyfikacji na makrostrukturę (kryształy równoosiowe) i właściwości mechaniczne. Potwierdzono oddziaływanie aktywnych składników obecnych w stopach niklu i materiale filtrów. Szczególnie silny efekt rozdrobnienia makrostruktury kryształów równoosiowych uzyskano dla stopu MAR-247, który zawiera najbardziej aktywne chemicznie dodatki Hf, Ta i Nb. Opracowano hipotetyczny model modyfikacji powierzchniowej i objętościowej. Stwierdzono istotny wpływ temperatury odlewania stopu na efekt modyfikowania. Efekt modyfikowania jest szczególnie widoczny przy temperaturze odlewania poniżej 1440°C.

2

Effect of technological parameters on structure of castings made from IN-713C nickel alloy

Binczyk F., Śleziona J., Szymszal J., Gradoń P.

Archives of Foundry Engineering

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2011

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Vol. 11, iss. 4

9-12

EN

The work includes studies to determine the significance of the effect of selected technological parameters of moulding and casting conditions on the macrostructure of IN-713C cast nickel alloy. Two-level, fractional 24-1 experiment was carried out, requiring eight experiments. The evaluation covered the number of grains per 1mm2 of the sample surface, the average grain surface area, and the shape index. Macrostructure of test castings indicates a positive effect of combined surface and bulk inoculation treatment, with the effect of surface inoculation prevailing as regards its importance. Statistically significant effect on the number and surface of grains have in descending order: surface modification, bulk modification and temperature of alloy pouring.

3

Ceramic filters for bulk inoculation of nickel alloy castings

Binczyk F., Śleziona J., Gradoń P.

Archives of Foundry Engineering

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2011

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Vol. 11, iss. 3 spec.

29--32

EN

The work includes the results of research on production technology of ceramic filters which, besides the traditional filtering function, play also the role of an inoculant modifying the macrostructure of cast nickel alloys. To play this additional role, filters should demonstrate sufficient compression strength and ensure proper flow rate of liquid alloy. The role of an inoculant is played by cobalt aluminate introduced to the composition of external coating in an amount from 5 to 10 wt.%. The required compression strength (over 1MPa) is provided by the supporting layers, deposited on the preform, which is a polyurethane foam. Based on a two-level fractional experiment 24-1, the significance of an impact of various technological parameters (independent variables) on selected functional parameters of the ready filters was determined. Important effect of the number of the supporting layers and sintering temperature of filters after evaporation of polyurethane foam was stated.

4

Macrostructure of IN-713C superalloy after volume modification

Binczyk F., Śleziona J.

Archives of Foundry Engineering

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2009

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Vol. 9, iss. 2

105-108

EN

The study discusses the results of the preliminary investigations of the process of volume modification of nickel and cobalt superalloys. The investigations were carried out on an IN-713C alloy. As an inoculant, cobalt aluminate CoAl2O4 in composition with aluminium powder and zircon flour was used. Experiments included the use of inoculant-coated filters and inoculant placed on and between the filters. As a criterion for evaluation of the modification effect, the macrostructure produced in a stepped test casting was used. It has been concluded that the modification effect depends, first of all, on the pouring temperature and on the time of contact between the liquid alloy and inoculant. Compared with the non-modified alloy, which has columnar grains in its structure, the refining treatment gave very fine and equiaxial grains. The higher was the cooling rate (or the smaller was the thickness of the step), the finer were the equiaxial grains.