Characteristic of electrolytic composite layers containing aluminium in nickel matrix after heat treatment
Iwona Napłoszek-Bilnik, Antoni Budniok, Edward Rówiński, Eugeniusz Łągiewka Uniwersytet Śląski, ul. Bankowa 12, 40-007 Katowice
Annals 4 No. 9, 2004 pages 79-82
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abstract The influence of the presence of Al powder in the galvanic bath on the chemical composition of Ni+Al layers was investigated. The electrodeposition processes was carried out at the temperature of 293 K and current density jdep = 200÷ ÷450 mA/cm2. It was stated, that Al percentages increase with an increase in the amount of Al powders in the bath and reach the value 8÷44% for Al. The surface morphology of the coatings was examined by means of a scanning microscopy (XPS- -method).The thickness of the coatings was estimated using microscope method on the base of cross-sectional images of the coatings (the thickness of Ni+Al coatings was 20÷50 μm). Electrodeposited Ni+Al composite layers were studied by Auger and photoelectron spectroscopies. Slight contents of oxygen, sulphur, phosphorus and carbon were present in addition to the main elements i.e. nickel and aluminium. X-ray diffraction method was used to determine phase composition of the layers and the atomic absorption spectrometry was applied to specify their chemical composition. The size of the nickel crystallites has been determined from the half-widht of the diffraction peaks (27 nm). The thermal treatment of the layers in 900°C/12 h in argon atmosphere changes a surface morphology and leads to produce a new kind of materials. They contain Ni2Al3, Ni3Al, NiAl phases embedded in the nickel matrix. 24-houred thermal treatment in 900°C leads to stabilization of the system with the formation of AlNi3 phase. The mechanism of incorporation of solid particles into to the layers structure was explained basing on Ni2+ adsorption/desorption processes on the metal powder. Key words: composite layers, intermetallic phase, aluminium