PROPERTIES OF COMPOSITE COATINGS TRANSFORMED FROM NICKEL ELECTRODEPOSITS CONTAINING SILICON PARTICLES

Composite (Ni) + Ni3Si coatings on C45 steel-substrate could be easily developed via three-step technology: electrodeposition of nickel interlayer, sediment co-deposition of Ni+Si and subsequent vacuum annealing at 980 degrees C for 5 h. The results of hardness measurements showed that as-plated Ni+Si coating was 1.7 times harder than the electrodeposited Ni coating, but the hardest was (Ni) + Ni3Si coating (820 HV) due to the presence of the super hard Ni3Si phase. At 1000 degrees C, (Ni) + Ni3Si coatings followed parabolic oxidation kinetic. During oxidation a thin continuous SiO2 layer formed below a layer of NiSiO3. After 100 h at 1000 degrees C a mass gain for (Ni) + Ni3Si coating was about 6 times lesser than for nickel coating. The wear mass loss of the (Ni) + Ni3Si coatings was approximately 2.5 times smaller than for as-plated Ni and Ni+Si coatings. The oxidised for 50 h (Ni) + Ni3Si coatings containing hard and wear-resistant SiO2 particles also showed smaller wear mass loss than Ni and Ni + Si coatings.