|KAFRÍK Ján||Fakulta Priemyselných Technológií, TnUAD|
|Spoluautoři KIANICOVÁ Marta, TRNÍK Jaroslav, DVOŘÁČEK Ondřej|
Hot corrosion behaviours of diffusion and Cr modified diffusion coatings are compared in the paper. Diffusion aluminide coatings are applied on nickel superalloy, creating a protective heat-activated Al2O3 layer, which acts as a protective barrier. The key to the success of Cr in inhibiting corrosion lies in the fact that Cr2O3 can dissolve to form several valence states and that the solubility in basic melt is oxygen pressure dependent, the result is a positive solubility gradient. Since Cr in the modified aluminide coatings is present in both, precipitates and Ni solid solution, it should prevent martensitic transformation of nickel rich β – NiAl. Although Cr increases Al activity in Ni-Al system it should tolerate greater Al depletion before NiO begins to form on the surface. Hot corrosion is the accelerated oxidation of a material at elevated temperature induced by a thin film of fused salt deposit. Samples from superalloys were coated by the method out – of – pack. Corrosive environment was created with help of tablets Na2SO4 at temperature 920 °C at Silesian University of Technology in Katowice, Poland. Hitachi SEM with EDX microanalysis was used to analysis of surfaces and cross –sections of the samples.