Structure of Ni-Si3N4 coatings deposited by the electrochemical method
Magdalena Kowalewska, Maria Trzaska Politechnika Warszawska, Wydział Inżynierii Materiałowej, ul. Wołoska 141, 02-507 Warszawa
Annals 3 No. 6, 2003 pages 3-7
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abstract Results of investigations of the influence of the electric current densities and the bath mixing on the structure and efficiency of the deposition of nickel and composite coatings Ni-Si3N4 on the steel substrate are presented in this paper. The Ni layers have been deposited in the Watts bath but the composite layers have been deposited in the Watts bath containing 5 g/dm3 of Si3N4 powder. In order to have the possibility of obtained results comparisons both Ni as well as Ni-Si3N4 layers have been deposited in identical conditions, i.e., the same velocity of bath mixing, same densities of electric current changed in the range 0.5÷6 A/dm3 and next at constants current density 3 A/dm2 but various velocities of bath mixing that have been taken from the interval 300÷600 turns/min. Influence of the current densities on the efficiency of the Ni and Ni-Si3N4 layers deposition are illustrated in Figure 2. Influences of the current densities on the structure of Ni layers are presented in Figures 3 and 4 and in the case of Ni-Si3N4 layers they are given in Figures 5 and 6, respectively. The rate of the bath mixing velocities and structures of composite layers are compared in Figure 7. The realized investigations have showed that the efficiency of the Ni and Ni-Si3N4 layers deposition takes the very high level which is of order 82÷99%. Moreover, it has been identified that the current density and the bath mixing velocity have import influence on the distribution of the disperse phase within the composite coatings and on its content in the whole deposited material. Key words: nickel coating, composite coating, structure, electrochemical method