Crystallization behavior of plasma-sprayed lanthanide magnesium hexaaluminate coatings

Abstract

LaMgAl₁₁O₁₉ thermal barrier coatings (TBCs) were prepared by atmospheric plasma spraying. The crystallization behavior of the coatings and the synthesis mechanism of LaMgAl₁₁O₁₉ powders were researched. The results showed that the plasma-sprayed coatings contained some amorphous phase, and LaMgAl₁₁O₁₉ powders were partially decomposed into Al₂O₃, LaAlO₃, and MgAl₂O₄ in the plasma spraying process. The amorphous phase was recrystallized at a temperature of approximately 1174.9°C, at which level the decomposed Al₂O₃, LaAlO₃, and MgAl₂O₄ reacted again. The resynthesis temperature of LaMgAl₁₁O₁₉ in the plasma-sprayed coatings was lower than that of LaMgAl₁₁O₁₉ in the original raw powders. The synthesis mechanism of LaMgAl₁₁O₁₉ powders can be summarized as follows: during the first part of the overall reaction, La₂O₃ reacts with Al₂O₃ to form LaAlO₃ at approximately 900°C, and then LaAlO₃ further reacts with Al₂O₃ and MgAl₂O₄ to produce LaMgAl₁₁O₁₉ at approximately 1200°C.

Keywords

thermal barrier coatings / hexaaluminates / plasma spraying / crystallization

References

[1] Zhu RX, Liu ZG, Ouyang JH, Zhou Y. Preparation and characterization of LnMgAl₁₁O₁₉ (Ln=La, Nd, Gd) ceramic powders. Ceram. Int., 2013, 39(8): 8841.

[2] Kelly M, Singh J, Todd J, Copley S, Wolfe D. Metallographic techniques for evaluation of thermal barrier coatings produced by electron beam physical vapor deposition. Mater. Charact., 2008, 59(7): 863.

[3] Park JG, Cormack AN. Defect energetics and nonstoichiometry in lanthanum magnesium hexaaluminate. J. Solid State Chem., 1997, 130(2): 199.

[4] Wang JW, Tian ZJ, Xu JG, Xu YP, Xu ZS, Lin LW. Preparation of Mn substituted La-hexaaluminate catalysts by using supercritical drying. Catal. Today, 2003, 83(1–4): 213.

[5] Gadow R, Lischka M. Lanthanum hexaaluminate — novel thermal barrier coatings for gas turbine applications — materials and process development. Surf. Coat. Technol., 2002, 151–152, 392.

[6] Friedrich C, Gadow R, Schirmer T. Lanthanum hexaaluminate: a new material for atmospheric plasma spraying of advanced thermal barrier coatings. J. Therm. Spray Technol., 2001, 10(4): 592.

[7] Wang YH, Liu ZG, Ouyang JH, Liu HZ, Zhu RX. Preparation and thermophysical properties of LaMgAl₁₁O₁₉-Yb₃Al₅O₁₂ ceramic composites. Ceram. Int., 2011, 37(7): 2489.

[8] Zhang JF, Zhong XH, Cheng YL, Wang Y, Xu ZH, Chen XL, Ma HM, Zhao Y, Cao XQ. Thermal-shock resistance of LnMgAl₁₁O₁₉ (Ln=La, Nd, Sm, Gd) with magnetoplumbite structure. J. Alloys Compd., 2009, 482(1–2): 376.

[9] Chen XL, Zhao Y, Gu LJ, Zou BL, Wang Y, Cao XQ. Hot corrosion behaviour of plasma sprayed YSZ/LaMgAl₁₁O₁₉ composite coatings in molten sulfate-vanadate salt. Corros. Sci., 2011, 53(6): 2335.

[10] Cao XQ, Zhang YF, Zhang JF, Zhong XH, Wang Y, Ma HM, Xu ZH, He LM, Lu F. Failure of the plasma-sprayed coating of lanthanum hexaluminate. J. Eur. Ceram. Soc., 2008, 28(10): 1979.

[11] Aruna ST, Balaji N, Rajam KS. Phase transformation and wear studies of plasma sprayed yttria stabilized zirconia coatings containing various mol% of yttria. Mater. Charact., 2011, 62(7): 697.

[12] Wang YH, Ouyang JH, Liu ZG. Preparation and thermo-physical properties of La_1−xNd_xMgAl₁₁O₁₉ (x=0, 0.1, 0.2) ceramics. J. Alloys Compd., 2009, 485(1–2): 734.

[13] Bansal NP, Zhu DM. Thermal properties of oxides with magnetoplumbite structure for advanced thermal barrier coatings. Surf. Coat. Technol., 2008, 202(12): 2698.

[14] Zhang YF, Li Q, Ma XF, Cao XQ. Synthesis and high-pressure sintering of lanthanum magnesium hexaaluminate. Mater. Lett., 2008, 62(6–7): 923.

[15] Liu HZ, Liu ZG, Ouyang JH, Wang YM. Thermo-optical properties of LaMg_1−xNi_xAl₁₁O₁₉ (0≤x≤1) hexaaluminates for metallic thermal protection system. Mater. Lett., 2011, 65(17–18): 2614.

[16] Chen XL, Zhang YF, Zhong XH, Xu ZH, Zhang JF, Cheng YL, Zhao Y, Liu YJ, Fan XZ, Wang Y, Ma HM, Cao XQ. Thermal cycling behaviors of the plasma sprayed thermal barrier coatings of hexaluminates with magnetoplumbite structure. J. Eur. Ceram. Soc., 2010, 30(7): 1649.

[17] Vaßen R, Jarligo MO, Steinke T, Mack DE, Stöver D. Overview on advanced thermal barrier coatings. Surf. Coat. Technol., 2010, 205(4): 938.

[18] Zhou H, Li F, He B, Wang J, Sun BD. Nanostructured yttria stabilized zirconia coatings deposited by air plasma spraying. Trans. Nonferrous Met. Soc. China, 2007, 17(2): 389.

[19] van Zyl A, Thackeray MM, Duncan GK, Kingon AI, Heckroodt RO. The synthesis of beta alumina from aluminium hydroxide and oxyhydroxide precursors. Mater. Res. Bull., 1993, 28(2): 145.

[20] Stumpf HC, Russell AS, Newsome JW, Tucker CM. Thermal transformations of aluminas and alumina hydrates. Ind. Eng. Chem., 1950, 42(7): 1398.

[21] Ozawa M, Onoe R, Kato H. Formation and decomposition of some rare earth (RE=La, Ce, Pr) hydroxides and oxides by homogeneous precipitation. J. Alloys Compd., 2006, 408–412, 556.

[22] Neumann A, Walter D. The thermal transformation from lanthanum hydroxide to lanthanum hydroxide oxide. Thermochim. Acta, 2006, 445(2): 200.

[23] Esaka T, Moto-ike K. CO₂ absorption and desorption of Bi₂O₃-La₂O₃ powders prepared by mechanical synthesis. Mater. Res. Bull., 2004, 39(11): 1581.

[24] Esaka T, Motoike K. Absorption and desorption of carbon dioxide in the rare earth oxide-doped Bi₂O₃ powder. J. Alloys Compd., 2006, 408–412, 480.

[25] Gschneidner KA, Bünzli J C, Pecharsky V K. Handbook on the Physics and Chemistry of Rare Earths, 2011, Netherlands, North Holland, 120.

[26] Shirsat AN, Ali M, Kaimal KNG, Bharadwaj SR, Das D. Thermochemistry of La₂O₂CO₃ decomposition. Thermochim. Acta, 2003, 399(1–2): 167.

[27] Béguin B, Garbowski E, Primet M. Stabilization of alumina by addition of lanthanum. Appl. Catal., 1991, 75(1): 119.

[28] Temuujin J, Jadambaa T, Mackenzie KJD, Angerer P, Porte F, Riley F. Thermal formation of corundum from aluminium hydroxides prepared from various aluminium salts. Bull. Mater. Sci., 2000, 23(4): 301.

[29] Zuzjaková Zeman P, Kos Non-isothermal kinetics of phase transformations in magnetron sputtered alumina films with metastable structure. Thermochim. Acta, 2013, 572, 85.