Mechanical milling prepared ultrafine Al2O3 particles utilized in brush plating Ni-P-Al2O3 coatings and influence of heat treatment to the performance of the coatings

In this paper, ultrafine Al2O3 particles were prepared by mechanical milling, and Ni-P-Al2O3 composite coatings were plated on Q235 steel substrates by brush-plating, which plating solutions were containing different concentrations Al2O3 particles. The morphology, phase and particle size distribution of the as-prepared Al2O3 particles, and the properties of the coatings after heat treatment were investigated. The results show that, the morphology of the as-prepared Al2O3 particles were spherical and almost size under 200nm, the coatings were uniformly thickness and the Al2O3 particles were uniformly dispersed in the coatings. Heat treatment could improve the performances of the brush-plating Ni-P-Al2O3 layers. After 1 hour heat treatment in 400 degrees C, the layer which phosphoric content about 2.3wt% had high rigidity, good abrasion-resistance and adhesion strength, and the layer which phosphoric content about 10.1wt% has good erosion-resistance after 1h heat treatment in 600 degrees C.