Abstract
Chromium nitrides CrXN have attracted research interest due to their excellent wear and corrosion properties when are deposited on steels. Nevertheless, due to the considerable difference between CrXN and steel expansion coefficients, microcracks and delamination are still persistent problems. In this regard, this research addressed the generation of CrNX nanolayers, through an ion nitriding process, carried out on hard chromium coated AISI 1045 steel. The effect of nitriding temperature (500°C-550°C) and nitrogen content in plasma (25, 50, and 75%) on corrosion performance and layer characteristics were studied. Grazing Incidence X-ray Diffraction analysis revealed that modified surfaces are composed of nanolayers, constituted by a mixture of CrN, Cr2N, Cr, and Fe4N. Rietveld quantification shows that the fraction of chromium nitrides in the region analyzed increased with increasing both temperature and nitrogen content in plasma, resulting CrN as the predominant phase for all evaluated conditions. The electrochemical behavior of the modified nanolayers was studied by potentiodynamic polarization technique, revealing an enhancement in corrosion performance of chromium coated 1045 steel by the nitriding treatment, showing a corrosion current density 10 times lower than the untreated sample and more positive corrosion potentials for the nitrided samples concerning chromium coated 1045 steel.
Highlights
Specific properties such as high corrosion resistance and excellent wear performance have been required through time in metallic components used in food, metalworking, and electronics industry
The results showed an improvement in corrosion resistance, in 3.5 wt% NaCl solution
Nanolayers composed of a mixture of nitrides were developed through short time and relatively low temperatures (500 °C and 550 °C) plasma nitriding process on hard chromium coated AISI 1045 steel
Summary
Specific properties such as high corrosion resistance and excellent wear performance have been required through time in metallic components used in food, metalworking, and electronics industry. As well as Taktak et al.[22] who studied the ionic nitriding process in AISI 52100 and 8620 steels coated with hard chromium, using different gas mixtures, revealing an improvement in the wear properties due to the formation of CrN and Cr2N. This research is based on the formation of nanolayers composed mainly of corrosion-resistant CrxN; it is intended to show that the corrosion resistance of CrxN can be efficient at a short time and low temperature at the nitriding process These treatment conditions could result in a more efficient and profitable nitriding process with a high possibility for industrial applications (e.g. fuel cells bipolar plates or diluting magnetic semiconductors). As corrosion resistance is related to the crystalline phases present on the surface, phases on nitrided samples were identified using Grazing Incidence X-ray Diffraction (GIXRD) with incidence angles set at 0.5 and 5°. The penetration depth of the X-ray during XRD analysis, was estimated by Equation 123, within the region of the most intense peaks in the patterns, assuming a location at 2θ angles of 43.65° for the main reflection of CrN and 44.58° for the main reflection of Cr-α, different types of CrxN is studied, as well as its influence on corrosion resistance of coated steel
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