Kinetics of the deposition of composite coatings Ni-P-Si3N4
Anna Wyszyńska, Maria Trzaska Politechnika Warszawska, Wydział Inżynierii Materiałowej, ul. Wołoska 141, 02-507 Warszawa
Annals 3 No. 6, 2003 pages 8-11
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abstract The paper is aimed on investigations of the influence of the temperature and mixing intensities on the deposition velocity and the microstructure of Ni-P surface coatings and composite coatings Ni-P-Si3N4, manufactured by the method of chemical reduction. The deposition processes of Ni-P layers have been realized in the electrolyte bathes containing NiCl2, NaH2PO2, Na3C6H5O7 and 5 g of the Si3N4 powder in the case of the Ni-P-Si3N4 layers, respectively. The coating processes of Ni-P and Ni- P-Si3N4 layers have been performed in identical conditions at the constant speed of the bath mixing performed with the mechanical mixer with 400 turns/min and at various temperatures of the process realization, namely at 80, 90 and 100°C. Next, the processes have been repeated at the constant temperature but variable speeds of the bath mixing performed in the range 300÷600 turns/min of the mixer. Dependences of the velocity of the layer depositions of the temperature are presented in Figure 1. Structures in the cross sections of the composite coatings produced at various temperatures are shown in Figure 2. Influences of the bath mixing intensities on the velocity of nickel and composite coatings are illustrated in Figure 3. Structures in the cross sections of the deposited layers at various mixing intensities of the electrolyte bath are presented in Figure 4. Results of investigations presented in this paper have showed that the increase of the process temperature augments the deposition velocity both of the Ni-P as well as of the Ni-P-Si3N4 layers and increases the rate of the contents of the disperse phase in the composite material. On the other hand the increase of the bath mixing intensities leads to an increase of the contents of the ceramic phase in the composite materials with simultaneous decrease of their deposition velocities. Key words: composite coatings, kinetics, electroless process, microstructure