Aluminização via HAPC (>i<Halide Activated Pack Cementation>/i<) de cobre e liga de inconel modificada visando aplicação em ventaneiras de alto-forno

Abstract

The work has as objective the application of aluminization to improve the corrosion resistance of copper tuyeres, which were previously coated or not with a layer of Inconel 625. The process adopted was Pack Cementation Diffusion Coating (PCDC). This coating is applied in tuyeres for blast furnaces, which work under extreme conditions. In order to get closer to the industrial reality, 1020 steel and A1050 aluminum were used for the donor alloy. The substrates were pure copper and a Inconel 625 superficial weld above pure copper (Inco625s). Aluminum oxide was used as inert filler and the process activation was achieved with NH4Cl. The coatings obtained from four kinds of aluminum oxide, as inert filler in separated times, were studied. Thermodynamic calculus was made to evaluate the capacity to aluminize the copper and Inco625s substrates. The coating was analyzed by optical microscopy and Scanning Electron Microscopy (SEM) associated to Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD), Vickers microhardness test and a non-standardized abrasion test for comparison effects. Besides that, the growth kinetics of the coating was studied, which indicated an overall parabolic growth with a similar activation energy for both cases, using pure copper substrate and Inco625s. The thermodynamic calculus showed the possible reactions to deposit the donor alloy on the substrate. The hardness of the coating obtained was higher than that of the substrate. Three kinds of the aluminum oxides studied have influenced negatively on the process, inducing an instability in the coating when exposed to open air. Only one kind of aluminum oxide has proved fit to be used in the coating process, thus being used as inert filler in the aluminization of the samples for wear resistance and kinetics analysis.