PSI - Issue 10

I. Georgiopoulos et al. / Procedia Structural Integrity 10 (2018) 280–287 I. Georgiopoulos et al. / Structural Integrity Procedia 00 (2018) 000 – 000

286

7

Table 2. Overview of the thermal cycling performance of the TBC tested.

Nr of long cycles @1200 o C

Nr. of short cycles @1200 o C

Nr of long cycles @1100 o C 14 (no spallation)

Nr. of short cycles @1100 o C 57 (no spallation)

System

Nimonic/NiCrAlY(APS)/YSZ(SPS)

3 (spallation)

36 (spallation)

Nimonic/NiCrAlY(APS)/YSZ(SPS)/LA(SPPS)

4 (spallation)

40 (spallation)

14 (no spallation)

57 (no spallation)

4. Conclusions

LaAlO 3 was used as over layer in multi-layered TBC systems. The additional thermal sealing provided by LaAlO 3 along with its lower fracture toughness improved the TBC performance during thermal cycling. SPS and SPPS thermal spray techniques proved effective for the deposition of high quality LaAlO 3 perovskite oxide coatings using liquid feedstocks. Use of precursor solutions and suspension materials provide the advantage of using nano-sized materials to develop coatings with unique microstructure, low porosity levels and microcrack free coatings. Furthermore, LaAlO 3 perovskite synthesis by a chemical reaction occurring during the liquid precursor materials flight within the plasma flame and subsequent coating deposition in a single step procedure is verified by using the SPPS technique. The effect of the deposition of LaAlO 3 over the YSZ was assessed, on the thermal cycling performance at both 1100 o C and 1200 o C. At 1100 o C the LaAlO 3 over layer does not affect the thermal cycling performance up to 14 long (ca. 350 h at 1100 o C) as well as after 57 short (ca. 57 h at 1100 o C) cycles. At 1200 °C the LaAlO 3 over-layered TBC performed slightly better compared to the not over-layered samples, indicating a satisfactory potential of LaAlO 3 perovskite over layers, worthing further investigation in the near future.

Acknowledgements

Financial support by «THEBARCODE - Development of multifunctional Thermal Barrier Coatings and modeling tools for high temperature power generation with improved efficiency» FP7 -NMP-2012-SMALL-6, Collaborative project.

References

Bakan, E., Vaßen, R., 2017. Ceramic top coats of plasma-sprayed thermal barrier coatings: materials, processes, and properties. Journal of Thermal Spray Technology 26, 992-1010. Cao, X.Q., Vassen, R., Jungen, W., Schwartz, S., Tietz, F., Stöver, D., 2001. Thermal stability of lanthanum zirconate plasma-sprayed coating. Journal of the American Ceramic Society 84, 2086-2090. Chen, X., Zhao, Y., Huang, W., Ma, H., Zou, B., Wang, Y., Cao, X., 2011. Thermal aging behavior of plasma sprayed LaMgAl11O19 thermal barrier coating. Journal of the European Ceramic Society 31, 2285-2294. Clarke, D.R., Oechsner, M., Padture, N.P., 2012. Thermal-barrier coatings for more efficient gas-turbine engines. MRS Bulletin 37, 891-898. Fu, M., Darolia, R., Gorman, M., Nagaraj, B.A., 2011. Thermal barrier coating systems including a rare earth aluminate layer for improved resistance to CMAS infiltration and coated articles, US8062759 B2, US 11/964,953. Gadow, R., Lischka, M., 2002. Lanthanum hexaaluminate - novel thermal barrier coatings for gas turbine applications - materials and process development. Surface and Coatings Technology 151-152, 392-399. Georgiopoulos, I., Marathoniti, E., Vourdas, N., Andreouli, K., Stathopoulos, V., 2014. Comparative study on liquid plasma sprayed lanthanum aluminate oxide coatings using different feedstock materials for potential TBC application, 25th Advanced Aerospace Materials and Processes (AeroMat) Conference and Exposition, ASM, Orlando, Florida, USA. Marathoniti, E., Vourdas, N., Georgiopoulos, I., Trusca, O.D, Trusca, I., Andreouli, C., Stathopoulos, V.N., 2014. Development of LaAlO3-based thermal barrier coatings by solution precursor thermal spray, International Conference on Material Technologies and Modeling-MMT 2014 Ariel, Israel, pp. 195-205. Ovanesyan, K.L., Kuzanyan, A.S., Badalyan, G.R., Yeganyan, A.V., Sargsyan, R.V., Kuzanyan, V.S., Petrosyan, A.G., Stathopoulos, V., 2014. Preparation and investigation of rare earth magnesium hexaaluminate solid solutions. Journal of Contemporary Physics (Armenian Academy of Sciences) 49, 220-227. Padture, N.P., Gell, M., Jordan, E.H., 2002. Thermal barrier coatings for gas-turbine engine applications. Science 296, 280-284. Schaper, H., Doesburg, E.B.M., Van Reijen, L.L., 1983. The influence of lanthanum oxide on the thermal stability of gamma alumina catalyst supports. Applied Catalysis 7, 211-220.