Hot corrosion studies on Ni-base superalloy at 650 degrees C under marine-like environment conditions using three salt mixture (Na2SO4 + NaCl + NaVO3)

摘要

The oxidation behavior of GTMSU718 alloy with 87.5 wt.% Na2SO4 + 5 wt.% NaCl + 7.5 wt.% NaVO3 (3SM) was studied at 650 degrees C. Cyclic oxidation studies with 3SM show more weight gain than 2SM (90 wt.% Na2SO4 + 10wt.% NaCl). It indicates that NaVO3 accelerates the oxidation behavior. Isothermal studies show a repetitive NaVO3 formation by combination of V2O5 and Na2SO4 until Na2SO4 is exhausted. Cr depletion layer occurs due to formation of Cr-sulphides, CrVO4 and liberation of Na2Cr2O7. Based on the detailed critical analysis, a plausible hot corrosion mechanism with 3SM was analysed to be basic fluxing mechanism, in parallel with sulphidation followed by oxidation. (C) 2016 Elsevier Ltd. All rights reserved.