Comportamento tribocorrosivo de revestimento de NiP-Al2O3 sobre o aço AISI/SAE 1045

Abstract

The petroleum’s exploration has been huge importance economic, social, technological, and everthing that can influence should be verified. One of the fator that must be analyzed are the equipment used in deep waters, that had been every moment in contact with aggressive environment suffering corrosion’s action combined whit the wear. This association is called of tribocorrosion, and a way for avoid who the equipment has its lifespan affected for this phenomenon, is a use of noble coating how is the case about nickel – phosphorus (NiP). The benefits that these coatings shows are deposition’s homogeneity, and with good corrosion resistance and wear, Although, the chemical deposition of NiP neither always happen as expected, giving rise to a porous coating. Two ways to try avoid this problem are the addition of hard particles in the coatings, like the case of alumina who is incorporated during the deposition, because alumina’s rightness improvement the properties of wear resistanve. The second way is to apply heat treatment the coating of NiP at 600ºC formin phases os Ni and Ni3P, through the interdiffusion layer that have goal eliminate pores and does not allow the substrate to be corroded in the presence of an aggressive environment. The purpose of this study was to evaluate the chemical deposition of NiP - Al2O3 by changing the particle size in two conditions: 0.3 μm and 1 μm and then to perform a 8 hour heat treatment at 600 °C to evaluate the tribocorrosive behavior, of the open circuit potential and perform the cyclic voltammetry test. The NiP chemical deposits were obtained under different conditions in order to compare the influence of the heat treatment and the diferentes sizes of the alumina particles. The morphological characterization of the coating was done through MEV analysis and EDS analysis to know the composition and the mapping of the studied region. The electrochemical characterization was performed by Open Circuit Potential and Potenciodynamic Curves. It was observed that the presence of the alumina significantly affects the thickness of the coating compared to the NiP as plated and that the heat treatment performed on a thin alumina sample creates passages so that the substrate reaches the top layer of the coating, it is also understood that the amount of alumina is inversely proportional to the amount of phosphor deposited in the coating.