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Nitrogen hardening of creep-resistant G-NiCr28W alloy

Pirowski Z., Wodnicki J., Gwiżdż A.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 3

79--84

EN

In the group of creep-resistant materials, most important are heat-resistant nickel-based alloys. The G-NiCr28W alloy subject to detailed examinations was observed to have two different austenite-like phases. In the interdendritic spaces of alloy matrix, the presence of another phase, also characterised by paramagnetic properties, was detected. Inside this interdendritic phase, local areas of a lamellar structure, composed of both of the above mentioned phases, were present. Nitrogen treatment was observed to raise the microhardness of both these phases. The presence of nitrogen made the regions of a lamellar structure disappear completely. Their place was occupied by precipitates dispersed in the matrix, and occasionally forming large clusters. It has been observed that cold work can harden the G-NiCr28W alloy to a very small degree only, in spite of the fact that hardness is increasing systematically with the increasing degree of cold work. The said alloy, when enriched with nitrogen added as an alloying element, is characterised by hardness higher than the hardness of its nitrogen-free counterpart. The value of hardness is increasing even more under the effect of low-degree cold work, although increasing further the degree of cold work seems to have no effect on hardness increase. The problem faced in nickel-based materials is the possibility of making defect-free castings from alloys with high nitrogen content. Alloys investigated in the present study were remelted, cast and subject to solidification under high nitrogen pressure in the furnace chamber. However, melting carried out under these conditions could not prevent the occurrence of non-metallic inclusions which, while being unable to pass to a riser, formed local clusters or even thin films, resulting in numerous microcracks or discontinuities encompassing large regions of the casting. This problem seems to be of major concern and is the first one to require prompt solution in the currently executed large research project.

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Heat-resisting alloys for hard surfacing and sealing pad welding

Wielgosz R. O.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 3 spec.

129--134

EN

The paper deals with heat-resisting alloys used to harden surfaces of elements operating in increased temperatures. It also deals with alloys used to seal cooperating surfaces of elements operating in the conditions of increased temperatures and aggressive utilities. Application methods and properties of thus obtained layers have been presented and adhesion of layers with matrix material has been assessed.

3

Wytwarzanie galwanicznych powłok platynowych na stopach żaroodpornych

Nawrat G., Simka W., Nieużyła Ł., Swadżba L.

Przemysł Chemiczny

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2006

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T. 85, nr 8-9

858-861

PL

Przedstawiono wyniki badań procesu platynowania galwanicznego stopów żaroodpornych stosowanych m.in. do wytwarzania elementów silników lotniczych. Zastosowano kąpiel galwaniczną opartą na kompleksowej soli platyny: cisdinitrodiaminoplatynie(II), [Pt(NH3)2(NO2)2], z dodatkiem substancji powierzchniowo czynnych powodujących zwiększenie wydajności prądowej procesu galwanicznego i jednocześnie pozwalających na podniesienie dopuszczalnej gęstości prądu bez pogorszenia przyczepności powłok do podłoża. Efektem zastosowania zmodyfikowanej kąpieli jest 4-krotne zwiększenie szybkości narastania grubości powłoki, co zwiększa przepustowość linii do platynowania elementów ze stopów żarowytrzymałych.

EN

The Pt bath based on cis-dinitrodiaminoplatinum(II) was modified with novel surfactant-moisturizer blends, 5 g/dm3, which enabled electroplating to be run at 30 A/m2 (4 × the conventional) to yield coatings 1.5–8 µm thick, uniform (15– 37% thick scatter), and well adhering to aviation turbine CrCo-Mo-W (IN-738) alloy blades. The surfactant-type alkylarylsulfonate alone, 10–15 g/dm3, the moisturizer alone, 0.2– 0.5 g/dm3, and a suitable blend of the two, raised the current efficiency by 25, ~25, and 36%, resp. Thorough defatting of the surface, electrolytical etch, chem. etch- up, activation by Ni precoating at 100×normal c.d., and optionally a mobile cathode are the pretreatment required to have Pt coatings of desired quality.

4

Problemy występujące przy spawaniu i naprawie spoin stali różnorodnych

Tasak E., Ziewiec A., Ziewiec K.

Archiwum Odlewnictwa

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2006

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R. 6, nr 21/2

221-227

PL

W artykule przedstawiono mechanizm powstawania warstwy odwęglonej przy obróbce cieplnej różnorodnych stali oraz wskazano, że obecność odwęglenia może być jedną z możliwych przyczyn awarii urządzeń energetycznych. Wykazano, że istnieje możliwość prognozowania zamian struktury SWC metodami obliczeniowymi.

EN

The paper presents mechanism of formation of decarburised layer during the heat treatment of dissimilar steels and it is showed that the decarburisation may be the one of possible reasons for failure of appliances in power industry. It is proved that it is possible to forecast the structure evolution of the heat affected zone by means of numeric methods.

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Ocena odporności na zmęczenie cieplne wybranych materiałów żaroodpornych

Kędzierska K., Tuleja J., Gawdzińska K.

Zeszyty Naukowe / Wyższa Szkoła Morska w Szczecinie

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2002

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nr 66

207-216

PL

Przedstawiono wyniki badań oceniających odporność na zmęczenie cieplne materiałów żaroodpornych o składzie chemicznym (% mas.): 17 ¸ 31% Cr i 18 ¸ 41% Ni. Próbki z doświadczalnych stopów poddano 75 cyklom zmęczeniowym. Odporność na zmęczenie cieplne oceniono na podstawie liczby tworzących się pęknięć. Opracowano zależność matematyczną między liczbą pęknięć, a liczbą cykli zmęczeniowych.

EN

Research results have been presented. These include the evaluation of the resistance to thermal fatigue of heat-resistant materials with the following chemical composition (% mass): 17% ¸ 31% Cr and 18 ¸ 41% Ni. Samples of tested alloys were subjected to 75 fatigue cycles. The resistance to thermal fatigue was evaluated on the basis of cracks formed. A mathematical relationship between the number of cracks and the number of fatigue cycles is given.