Al2O3 ceramic-Ni-Fe-Cr composite to the joining of ceramic with metals
Marek Barlak Politechnika Warszawska, Instytut Technologii Materiałowych, ul. Narbutta 85, 02-524 Warszawa
Annals 1 No. 1, 2001 pages 12-15
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abstract The paper presents the first results of the investigations of Al2O3 ceramic - Inconel 718 alloy composite (25%Al2O3-75% 718, 50%Al2O3-50% 718 and 75%Al2O3-25% 718 by volume) in Welding Department of Warsaw University of Technology. In the investigations we use the powders of alumina (Fig. 1) and the powders of 718 (Fig. 2). Fig. 3 shows the first model of ceramic-metal joint. The first investigations concerned the sintering process of each layer (process conditions - temperature: 1150ºC, time: 30 min, vacuum: 5•10−5 Tr, pressure: 200 kG, the diameter of samples: 10 mm and initial height of samples: 11,9 mm). During the sintering process stepped out the contraction of each layer (Fig. 4). The value of the contraction presents Fig. 5. The difference of the bulk density and material density is the reason of the contraction (Table 1). The composite mikrostructure after sintering process presents Fig. 6. The microhardness of each layer was calculated by means of the formula [4]. The average microhardness of Al2O3 ceramic is 800 μHV100 and the average microhardness of 718 alloy is 220 μHV100 (table 2). The calculation result shows Fig. 7. Figure 8 presents the joint of Al2O3 ceramic substrate/75% Al2O3-25% 718 layer. Fig. 9 shows the crack in ceramic substrate and Fig. 10 shows „lensshape” crack of ceramic substrate. On the ground of the investigations we can state, that: the obtaining of Al2O3 ceramic-718 alloy composite is possible, the contraction of each layer is during sintering process, the bulk density of materials is twice and three times smaller like solid material, each layers have homogeneous microstructure, good sintering degree without the porosity, the obtaining of correct Al2O3 ceramic substrate/75%Al2O3-25% 718 layer joint is possible. The next investigations will include: the investigation by scanning microscopy, X-ray diffraction, the analysis of the distribution of elements, the production of correct ceramic--gradient layer-metal joint and its optimisation (dimensions, chemical composition), the investigations of the boundaries, the investigations of mechanical strength, the trial of application.