Laser CVD Process for High Speed Deposition of YSZ Films

Abstract

Thick oxide coatings have wide ranged applications such as oxidation protection, abrasives and thermal barrier coating (TBC). Yttria stabilized zirconia (YSZ) has been used for TBC in gas turbines. Generally, atmospheric plasma spray (APS) and electron-beam physical vapor deposition (EB-PVD) have been utilized in practical applications. Although chemical vapor deposition (CVD) provides high quality coatings, the deposition rate of CVD could have been too small for TBCs. We have recently developed a new laser CVD process achieving an extremely high deposition rate up to 660 ım/h for YSZ coatings on Al2O3 substrates and Ni-based super alloy substrates using Zr(dpm)4 and Y(dpm)3 precursors. An Nd:YAG laser with a high power of 250 W was introduced in a CVD chamber as a defocused beam in a diameter of 20mm covering a whole substrate surface. The YSZ coatings had a well-grown columnar structure with significant (200) orientation. Other oxides such as Y2O3, Al2O3 and TiO2 films were also prepared by laser CVD at high deposition rates around 1 mm/h.