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Long-term Annealing of NiCrAlY LENS Coating on 316L Steel

Szymański Krzysztof K.

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 4

116--120

EN

This article presents the results of a research on the behavior of NiCrAlY coating obtained by the LENS method on austenitic stainless steel type 316L under long-term annealing conditions at 1000°C for 25, 100 and 250 hours. The morphology of the NiCrAlY layer as a function of annealing time and temperature was characterized. The chemical composition and distribution of alloying elements were evaluated using scanning microscopy and micro-area chemical composition analysis. It was revealed that NiCrAlY coatings deposited by LENS method are characterized by good metallurgical quality. The long-term annealing of the NiCrAlY coating led to microstructural changes in the form of the disappearance of the original dendritic structure and the formation of a solid solution of nickel with chromium and a small amount of aluminum, as well as chromium α-Cr precipitates and Ni-Y-type phases. The effect of increasing iron concentration in the coating due to diffusion-to-core processes was also found.

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Influence of heat treatment on microstructure of slurry aluminide coatings type TiAlSi obtained on TiAlCrNb alloy

Moskal G., Witala B., Rozmysłowska A.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 33, nr 2

204-210

EN

Purpose: Influence of heat treatment on microstructural changes in slurry TiAlSi coating deposited with 12.5% Si concentration on Ti48Al2Cr2Nb intermetallic alloy and investigation of the influence of Si addition on the structure of obtained coatings is a purpose of this paper. Design/methodology/approach: The research allowed identifying microstructural changes that took place during annealing at 950°C of the TiAlSi coating for 2 to 10h exposure in air. A scope of the research encompassed a microstructural analysis with the use of macro and micro investigation - LM, SEM microscopy, XRD phase analysis and EDS analysis. Findings: The investigation has shown that the thickness of the TiAlSi coatings in initial conditions and after a test was in a range from 30 to 40 ěm. The structure of the silicon-modified aluminide coatings is as following: the outer zone consisting of the TiAl3 phase and titanium silicides / the middle zone consisting of columnar titanium silicides in phase TiAl3 matrix / the inner zone consisting of TiAl2 phase. Basic changes were related to differences in thickness in sublayers. Research limitations/implications: The discussed research proves that main reason of much better protection of TiAlSi coated base alloy is related to high microstructure stability of Si modified in TiAl3 phases. In addition silicon decreases activity of titanium, and in consequence the susceptibility of Al to selective oxidation is much stronger. The presence of Si due to Ti-Si phase generation with high oxidation resistance is presented. Practical implications: The slurry method can be applied in aerospace and automotive industry as low-cost technology in production of aluminide coatings on intermetallics. Originality/value: New method of aluminide coatings deposition on TiAl alloys.

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Qualitative and quantitative description of microstructural stabillity of TiAlNb intermetallic alloy

Moskal G.

Inżynieria Materiałowa

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2008

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Vol. 29, nr 4

340-345

EN

The purpose of the investigation presented in the article is to determine the influence of temperature and time of annealing on the microstructure stability of the Ti-Al-Nb alloy based on intermetallic phases y+a2. The qualitative microstructural analyses on the alloy following the annealing at 900 and 950°C for up to 690 hours have been performed. The quantitative assessment of the influence of annealing parameters on the size and shape of the lamellar colonies and the size of the lamellae themselves, including digital image analysis (DIA), has been done. It has been proven that whereas the annealing process affects neither the size nor the shape of the colonies significantly, it has some bearing on the thickness of the lamellae of the particular phases. As far as the microstructural stability of the alloy is concerned, the applied treatment did not have a major impact on the degradation of the structure, which proved to be stable under these conditions. The only noted changes were the formation of new g phase grains and the changes in the thickness of the lamellae, while the size of the entire colony remained intact.

PL

Celem badań przedstawionych w artykule było określenie wpływu temperatury i czasu wygrzewania na stabilność mikrostruktury stopu Ti-Al-Nb na osnowie faz międzymetalicznych y + 0:2. Wykonano jakościowe badania mikrostrukturalne na stopie wygrzewanym w 900 i 950°C w czasie do 69(1 godzin. Wykonano ilościową ocenę wpływu parametrów wygrzewania na wielkość i kształt kolonii płytkowych oraz na wielkość samych płytek przy zastosowaniu m.in. metod automatycznej analizy obrazu. Stwierdzono, iż przeprowadzone wygrzewania nie wpływa zasadniczo na wielkość i kształt kolonii natomiast ma wpływ na grubość płytek poszczególnych faz. Z punktu widzenia stabilności mikrostrukturalnej stopu zastosowana obróbka nie wpłynęła na degradację struktury, która okazała się być stabilna w tyci warunkach. Jedynymi zaobserwowanymi zmianami było tworzenie się nowycl ziaren fazy y oraz zmiany grubości płytek, przy zachowaniu wymiarów całej kolonii płytkowej.