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Microstructural tests and hardness tests of surface layers of nodular cast iron GJS-350 made using the laser surface alloying process

Sacha Denis

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2021

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Vol. 65, No. 6

37--45

EN

The article presents test results concerning the microstructure and the hardness of a composite layer made on a substrate of nodular cast iron GJS-350 using the laser surface alloying method. The alloying agent used in the test was powdered titanium. The study consists of an overview of reference publications aimed to introduce the most important aspects concerning the issue subjected to analysis. The research part presents the methodology of tests as well as their results and analysis. Microscopic analysis revealed that the layer structure was fine-grained and highly homogenous, whereas hardness measurements revealed that the titanium-enriched layer was characterised by significantly higher micro-hardness than that of the base material.

PL

Artykuł przedstawia wyniki badań mikrostruktury i twardości wytworzonej warstwy kompozytowej na podłożu z żeliwa sferoidalnego GJS-350 metodą stopowania laserowego. Jako dodatku stopującego użyto tytanu w postaci proszku. Praca składa się z przeglądu literatury, który ma przybliżyć najważniejsze zagadnienia dotyczące analizowanego problemu. W części badawczej przedstawiono metodologię prowadzonych badań naukowych oraz uzyskane wyniki i ich analizę. Przeprowadzona analiza mikroskopowa pozwoliła ustalić, że wytworzona warstwa ma drobnoziarnistą strukturę o wysokiej jednorodności. Natomiast badania twardości potwierdziły, że warstwa wzbogacona w dodatek tytanu wykazuje znacznie wyższą mikrotwardość niż materiał podłoża.

2

In situ-formed, low-cost, Al-Si nanocomposite materials

Guba P., Gesing A.J., Sokolowski J., Conle A., Sobiesiak A., Das S. K.

Journal of Achievements in Materials and Manufacturing Engineering

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2017

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Vol. 84, nr 1

5--22

EN

Aluminum-Silicon (Al-Si) alloys are the “bread-and-butter” of the aluminum foundry industry being cast at an annual rate of over 2 million tonnes/year in North America for use mainly in transportation. Coarse microstructure of these alloys limits their specific mechanical properties and consequently their potential for vehicle lightweighting. Purpose: We report on a new family of cast Al-Si alloys producing in-situ formed nanocomposites of up to 25 vol.% ultrafine equiaxed silicon particles in Al alloy matrix which can be ductile, or reinforced by nano-scale spinodal constituents. Design/methodology/approach: The hypereutectic Al-Si-X alloy (A390) was melted, solidified and cooled on the novel High Pressure Die Casting Universal Metallurgical Simulator and Analyser Technology Platform (HPDC UMSA) at specific process parameters. The HPDC cast samples consecutively were solution treated and artificially aged to spheroidize the Si and to dissolve the intermetallics in Al(SS) and to re-precipitate them in the solid state as nano-sized spinodal structures. The heat treatment was performed using the High Temperature UMSA Technology Platform. Findings: The nano scale structure of these new materials gives them significantly improved strength, hardness, and wear resistance while retaining adequate toughness and ductility for applications in the transportation applications. Research limitations/implications: Desired composite nanostructures have been produced and characterized in-situ in small laboratory test samples. Practical implications: These new materials can be produced by conventional casting technologies such as continuous strip casting, or high-pressure die-casting from conventional low-cost Al-Si melts. Originality/value: These materials can be produced with a significantly higher volume fraction of ultrafine Si dispersoids than has been done to date in in-situ formed materials, while retaining and improving the density-specific mechanical properties.

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Microstructural Evolution During Laser Surface Alloying of Ductile Cast Iron with Titanium

Janicki D.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 4

2425--2431

EN

Diode laser surface alloying process was used to the in-situ synthesis of TiC-reinforced composite surface layers on the ductile cast iron substrate. The obtained composite surface layers were investigated using optical and scanning electron microscopy, and XRD diffraction. It was found that the morphology and fraction of TiC phase is directly dependent upon both the concentration of titanium in the molten pool and also the solidification rate. With increasing titanium content, the fraction of TiC increases, whereas the fraction of cementite decreases. The TiC phase promotes a heterogeneous nucleation of primary austenite grains, what reduces a tendency of cracking in the alloyed layers.

4

Experimental and Thermodynamic Study of Selected in-Situ Composites from the Fe-Cr-Ni-Mo-C System

Wieczerzak K., Bala P., Dziurka R., Stepien M., Tokarski T., Cios G., Gorecki K.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 2B

1241--1247

EN

The aim of the study was to synthesize and characterize the selected in-situ composites from the Fe-Cr-Ni-Mo-C system, additionally strengthened by intermetallic compounds. The project of the alloys was supported by thermodynamic simulations using Calculation of Phase Diagram approach via Thermo-Calc. Selected alloys were synthesized in an arc furnace in a high purity argon atmosphere using a suction casting unit. The studies involved a range of experimental techniques to characterize the alloys in the as-cast state, including optical emission spectrometry, light microscopy, scanning electron microscopy, electron microprobe analysis, X-ray diffraction and microhardness tests. These experimental studies were compared with the Thermo-Calc data and high resolution dilatometry. The results of investigations presented in this paper showed that there is a possibility to introduce intermetallic compounds, such as χ and σ, through modification of the chemical composition of the alloy with respect to Nieq and Creq. It was found that the place of intermetallic compounds precipitation strongly depends on matrix nature. Results presented in this paper may be successfully used to build a systematic knowledge about the group of alloys with a high volume fraction of complex carbides, and high physicochemical properties, additionally strengthened by intermetallic compounds.

5

On the character of matrix-reinforcing particle phase boundaries in MeC and MeB (Me= W, Zr, Ti, Nb, Ta) in-situ composites

Janas A., Kolbus A., Olejnik E.

Archives of Metallurgy and Materials

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2009

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Vol. 54, iss. 2

319-327

EN

In metal matrix composites (MMCs), the character of the matrix-reinforcing particle phase boundaries has very important effect on the utilisation properties of these materials. For some composites like Al/TiC, Al/TiB2, Ni3Al/TiC, AlSi/SiC and Za27/NiAl, the properties of these phase boundaries were discussed in detail in study [1]. From this study it follows that during the in-situ composite synthesis by SHSB route, the solidification process results in the formation of large internal stresses, due to differences that have been observed to exist in the values of the coefficients of thermal expansion and elastic modulus between the matrix and reinforcing particles [2,3]. According to A. Mortensen [4], the differences in the thermal expansion that occur between the matrix and the reinforcing phase increase the density of dislocations in the structure, which may lead to the formation of microcracks. Besides these effects, alien phases, formed additionally in the process of composite synthesis, may appear at the phase boundaries. These are usually the undesired phases, weakening the bond that should exist between the matrix and the reinforcing particle. Both alien precipitates and the stresses have an important effect on the character of the phase boundaries and, indirectly, on the mechanical properties of composites fabricated by SHSB route [5,6,7]. The application of modern research methods, e.g. high-resolution electron microscopy (HREM), enables better understanding of the phenomena taking place at the matrix-reinforcing particle phase boundary. This study describes the investigations that have been carried out to prove the presence of internal stresses in the in situ composites. They are meant to complete the results presented in [1]. The main aim of the present study was to investigate the character of the matrix-ceramic particle phase boundary in, fabricated by the SHSB method, new composites from the group of the "in situ" materials, i.e. Ni3Al/WC, Ni3Al/ZrC, Ni3Al/NbC, Ni3Al/NbB [8] as well as Ni3Al/TaC and Ni3Al/TaB. Like in [1], also in this case, the techniques used in investigations included electron microscopy, scanning microscopy and X-ray microanalysis.

PL

Charakter granic międzyfazowych osnowa – cząstka w kompozytach metalowych typu MMCs ma zasadniczy wpływ na właściwości użytkowe tych materiałów. Charakter tych granic dla niektórych kompozytów: Al/TiC, Al/TiB2, Ni3Al/TiC, Al-Si/SiC oraz Za27/NiAl zostały szczegółowo przedstawione w pracy [1]. Wynika z niej, że przy syntezie kompozytów "in situ" metodą SHSB, po procesie krystalizacji, powstają duże naprężenia wewnętrzne wynikajace z różnic wartości współczynników rozszerzalności termicznej, oraz modułów sprężystości osnowy i cząstek wzmacniających [2,3]. Według A. Mortensena [4] to niedopasowanie rozszerzalności cieplnej pomiędzy osnową a umocnieniem jest przyczyną wzrostu gęstości dyslokacji w strukturze, co w następstwie może prowadzić do powstawania mikropeknięć. Oprócz tego na granicy rozdziału, mogą pojawiać się obce fazy, powstające dodatkowo w procesie syntezy kompozytu. Są to fazy zwykle niepożądane, osłabiające wiązanie osnowa -cząstka wzmacniająca. Zarówno obce wydzielenia jak i naprężenia mają decydujący wpływ na charakter granicy fazowej czyli pośrednio na właściwości mechaniczne otrzymywanych ta metoda kompozytów [5,6,7]. Zastosowanie nowoczesnych metod badawczych, m.in. wysokorozdzielczej mikroskopii elektronowej HREM, pozwala poznać opisane zjawiska na granicy międzyfazowej osnowa-cząstka wzmacniająca. W niniejszej pracy przedstawiono badania potwierdzające występowanie naprężeń wewnetrznych w kompozytach "in situ". Uzupełniają one wyniki badań prezentowanych w pracy [1]. Głównym celem prezentowanej pracy jest badanie charakteru granic osnowa – cząstka ceramiczna w wytworzonych metodą SHSB, innych, nowych materiałach kompozytowych, z grupy kompozytów "in situ" t.j. Ni3Al/WC, Ni3Al/ZrC, Ni3Al/NbC, Ni3Al/NbB [8] oraz Ni3Al/TaC i Ni3Al/TaB. Podobnie jak w pracy [1], do badań wykorzystano metody mikroskopii elektronowej, mikroskopii skaningowej i mikroanalizy rentgenowskiej.