The subject of this master's thesis was an increase of the concentration of aluminum in the surface layer of steels 16Mo3, 13CrMo4 5, 10CrMo9-10 and X2CrNi18 9, and moreover, obtaining information on corrosion stability. The analysis specifically addresses the basic materials, namely steels in the base condition as well as in the aluminized condition, i.e. steel enriched with aluminium surface layer. The steels have been subjected to heat treatment using the aluminizing process in backfill in order to increase the amount of aluminium in the surface layer. The aluminizing process took place only in the gas phase using the solid mixture in the backfill. The used backfill as the means of aluminizing was a mixture of several types of powder consisting of 1% of Al by weight, 1% of NH4Cl by weight and 98% of Al2O3 by weight. The process was carried out at 900 ⁰C in a tube furnace and it lasted four hours.
After aluminizing process, we obtained information on the development of the microstructure, carried out hardness measurements and determined the corrosion properties by means of electrochemical methods. The electrochemical properties of the steels were determined by means of linear polarization measurements, potentiodynamic measurements and electrochemical impedance spectroscopy. The electrochemical testing methods have been performed in 0.1 M NaCl solution at room temperature.
Based on the results of the inspections, we examined and analysed the impact of the aluminizing on the behaviour of the handled steels with the ultimate objective of the assessment of the corrosive properties. The primary objective of the survey was to evaluate, on the basis of the electrochemical measurements carried out, the enriched surface in terms of improving the corrosion resistance.
Corrosion resistance of steels has increased with alumnization, except for stainless steel X2XrNi18-9 where it increased.