Fabrication and Characterization of Ni-Al_2O_3 Nano-Composite Coatings by Sediment Co-Deposition

Ni-Al2O3 nano-composite coatings were fabricated by sediment co-deposition (SCD) from Watt’s type electrolyte containing nano-Al2O3 particles without any additives. For comparison, Ni-Al2O3 nano-composite coatings were prepared by conventional electro-plating (CEP) under experimental conditions. Effects of process parameters, such as nano-Al2O3 concentration in plating solution, current density, stirring rate, and bath temperature, on nano-Al2O3 content in composite coatings were investigated. The distribution of elements in deposit, and the bonding strength between coating and substrate was analyzed by electron probe microanalyzer (EPMA) and auto-scratch apparatus, respectively. It is found that the nano-Al2O3 concentration in plating solution, current density and stirring rate are three main factors affecting the particles content in deposit, and played a key role in the formation of composite coatings. The nano-Al2O3 content in composite coatings increased with increasing of nano-Al2O3 concentration in plating solution, current density and stirring rate to reach a maximum value, and then reduced slightly. The contents of nano-Al2O3 particles in composite coatings by the SCD technique were higher than that by the CEP technique. The co-deposited nano-Al2O3 particles embedded uniformly in the Ni matrix. The coating was well adhesion with substrate. It is demonstrated that the SCD technique is an efficient approach for improving the nano-Al2O3 content in Ni-Al2O3 composite coatings.

Ni-Al2O3 nano-composite coatings were fabricated by sediment co-deposition （SCD） from Wart＇s type electrolyte containing nano-Al2O3 particles without any additives. For comparison, Ni-Al2O3 nano-composite coatings were prepared by conventional electro-plating （CEP） under experimental conditions. Effects of process parameters, such as nano-Al2O3 concentration in plating solution, current density, stirring rate, and bath temperature, on nano-Al2O3 content in composite coatings were investigated. The distribution of elements in deposit, and the bonding strength between coating and substrate was analyzed by electron probe microanalyzer （EPMA） and auto-scratch apparatus, respectively. It is found that the nano-Al2O3 concentration in plating solution, current density and stirring rate are three main factors affecting the particles content in deposit, and played a key role in the formation of composite coatings. The nano-Al2O3 content in composite coatings increased with increasing of nano-Al2O3 concentration in plating solution, current density and stirring rate to reach a maximum value, and then reduced slightly. The contents of nano-Al2O3 particles in composite coatings by the SCD technique were higher than that by the CEP technique. The co-deposited nano-Al2O3 particles embedded uniformly in the Ni matrix. The coating was well adhesion with substrate. It is demonstrated that the SCD technique is an efficient approach for improving the nano-Al2O3 content in Ni-Al2O3 composite coatings.