Avaliação de propriedades físicas e químicas de eletrodepósitos de Ni-W-P obtidos em célula Hull.

Abstract

The amorphous alloys of tungsten with iron group metals, obtained by electrodeposition have attracted increasing interest in recent years in view of its excellent properties for technological applications such as magnetic properties, mechanical properties, wear resistance and corrosion, among other. These properties are mainly related to composition and chemical homogeneity and the absence of defects associated with the crystalline state. Several authors have highlighted that these materials are potentially one of the most promising to replace the conventional hard chromium coatings, which for decades has distinguished itself worldwide as one of the most used because of its high hardness (greater than 800 Hv) and corrosion protection. The attainment of these alloys can be made by different techniques. However, electrodeposition has been one of the most used because it allows obtaining high-purity chemical deposits with different compositions and thicknesses and allows also take different types of substrates, having various geometric shapes. In general, these systems retain some unusual properties of tungsten, such as high corrosion resistance, hardness, low coefficient of expansion and high thermal conductivity, and resist any attack by mineral acid at room temperature. Most of the quotes on this subject are related to adjustments of electrolytes and operational parameters for obtaining good quality alloy in optimized conditions, leaving gaps in relation to obtaining those under industrial conditions. In general, the experiments are restricted to areas with small electrodes to be coated and electroplated made under very refined compared to the control of acquisition parameters. This is a practical limitation for use of these materials. In this study, we sought to obtain Ni-W-P alloys in a Hull cell on 1010 steel substrate from an electrolyte composition already established in the literature. Were made to the physical and chemical characterizations of the alloys investigated the effects of wide variation in current density on the chemical composition, surface morphology, corrosion resistance and hardness of the same.