Electrolytic production and heat-treatment of Ni-based composite layers containing intermetallic phases

The influence of the presence of Al powder in the galvanic bath on the chemical composition of Ni + Al layers was investigated. The electrodeposition process was carried out at a temperature of 293 K and a current density of jdep = 200-450 mA cm-2. 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 scanning microscopy (SEM method). The thickness of the coatings was estimated using microscope methods on the base of cross-sectional images of the coatings (the thickness of Ni + Al coatings was 150-320 μm). X-ray diffraction method was used to determine the phase composition of the layers. Quantitative chemical analysis of the coatings was determined by means of X-ray fluorescence method (XRF) and verified by atomic absorption spectroscopy (AAS). The size of the nickel crystallites has been determined from the half-width of the diffraction peaks (27 nm). The thermal treatment of the layers in 900 deg. C/12 h in argon atmosphere changes the surface morphology and leads to produce a new kind of materials. They contain Ni2Al3, Ni3Al, NiAl phases embedded in the nickel matrix. About 24 h thermal treatment in 900 deg. C leads to stabilization of the system with the formation of NiAl, AlNi3 phase. The mechanism of incorporation of solid particles into the layers' structure was explained based on Ni2+ adsorption/desorption processes on the metal powder