Role of Magnesia Stabilized Zirconia Dispersion on the Hot Corrosion Behaviour of NiCrAlY Plasma-Sprayed Coatings in Na2SO4+50 wt% V2O5 and Na2SO4+10 wt% NaCl Melts at 800 degrees C

摘要

In order to understand the possible role of magnesia stabilised zirconia (MSZ) on hot corrosion in graded thermal barrier coatings, plain and 25 and 50 wt% MSZ dispersed NiCrAlY coatings, developed using air plasma spray technique was examined by exposing them to Na2SO4 + 50 wt% V2O5 and Na2SO4 + 10 wt% NaCl environments at 800 A degrees C. The study shows that MSZ dispersion significantly increases the hot corrosion tendency of NiCrAlY coatings in both the environments and that the MSZ phase suffers destabilization into monoclinic ZrO2 in both the environments suggesting that it cannot be used for producing graded bond coats. Mg ions leach out from MSZ phase forming Mg3V2O8 and MgCl2 on exposure to vanadates and chlorides respectively. The study further demonstrates that chloride is more detrimental to the coatings than vanadate.