Composite coatings of nickel and ceramic particles prepared in two steps

A simple technique has been proposed in order to disperse a high vol.% of ceramic particles into a nickel matrix in two steps. A uniform film of ceramic particles was first electrophoretically deposited on an iron plate. Nickel was then electrodeposited in the second step onto the substrate covered with the film of these ceramic particles. Using 5 g/dm3 of particles in the electrophoretic bath, the two-step method enabled us to incorporate 63 and 67 vol.% of Al2O3 and BN particles, respectively, into the nickel matrix. Similarly, using a mixture of 5 g/dm3 of BN and 2.5 g/dm3 of Al2O3 particles in the electrophoretic bath, the proposed two-step method enabled us to incorporate 55.5 and 6.2 vol.% of BN and Al2O3 particles, respectively, into the nickel matrix. In the present investigation, the wear resistance of the coatings was examined under dry sliding conditions using the ball-on-disk configuration. For the reference, an iron plate was coated with the Ni/BN and Ni/Al2O3 composites in a single step. The content of BN and Al2O3 particles in these coatings were 18 and 8.4 vol.%, respectively. The wear experiments showed that, regardless of the method of preparation, the Ni/BN composite coatings had a better wear-resistant performance than the Ni/Al2O3 coatings. However, all three composite coatings prepared by the two-step method showed substantially better wear resistance than those prepared by the single-step method. It has been assumed here that the better anti-wear performance of the composite coatings prepared by the two-step method is due, not only to the higher volumetric content of the particles, but also to the manner in which these particles were incorporated within the metal matrix.