Perez-Mariano, J., Lau, K. H., Alvarez, E., Malhotra, R., Hornbostel, M., Krishnan, G., & Sanjurjo, A. (2008). Multilayer coatings for corrosion protection of coal gasifier components. Materials Chemistry and Physics, 112(1), 180-185.
Deposition of TiAlN/Nb, TiAlN/Ta, TiAlN/W and TiAlN/Zr multilayer coatings on 409 stainless steel was studied by CVD in a fluidized bed reactor (FBR-CVD). The coatings consisted of four TiAlN layers with individual thickness of 2.5–3.5 μm, and four metal interlayers with thicknesses in the range of 100–250 nm. The W interlayers suffered partial nitridation during the coating process and the resulting coatings had poor adhesion. Deposition of Zr through reduction of ZrI4 by H2 was found to be inefficient. Both TiAlN/Nb and TiAlN/Ta coatings showed good adhesion, but only TiAlN/Nb provided sulfidation resistance to 409 steel during exposure to simulated coal gas at 1173 K for 300 h. Though outward diffusion of Cr took place during the corrosion test, the results reported in this paper suggest that TiAlN/Nb coatings are promising candidates for corrosion protection of steels under typical coal gasifier conditions.