Chemical Solution Deposition of Protective Er2O3 and Y2O3 Coatings onto Stainless Steel for Molten Metal Casting using Metal-Nitrate Precursors

Chemical solution deposition (CSD) methods involvingthe thermaldecomposition of 5.0 M Er-(NO3)(3)center dot 5H(2)O and Y-(NO3)(3)center dot 6H(2)O precursorsolutions were employed to fabricate protective erbia and yttria coatingsonto stainless steel (SS304/SS316) coupons. The two techniques testedwere dip and spray coating, which were then compared to a commercialyttria spray (ZYP Coatings). It was determined that solution concentration,solvent choice, injection of Er2O3 and Y2O3 micropowder, and the annealing temperature/rampprofile were critical to the coatings' physical properties.For dip coatings, thicknesses were 1-20 mu m after twodipping/annealing cycles, and adhesion strength was similar to 1000 psi,increasing up to similar to 1300 psi if the SS coupons had preliminarysandblasting. Spray coatings from precursor solutions were reportedto have thicknesses of 20-80 mu m and adhesion strengthless than 500 psi (regardless of the coupon surface finish). Cross-sectionalviews of the coatings confirmed subsurface porosity, and XRD resultsindicated that the coatings were polycrystalline, with patterns typicalto that of cubic Er2O3 and Y2O3.

Automated summary

Chemical solution deposition (CSD) methods utilizing Er-(NO3)(3)center dot 5H(2)O and Y-(NO3)(3)center dot 6H(2)O precursor solutions were used to fabricate protective erbia and yttria coatings. Dip coatings had thicknesses of 1-20 mu m and adhesion strength similar to 1000 psi, while spray coatings had thicknesses of 20-80 mu m and adhesion strength less than 500 psi.