EFFECT OF RESIDUAL STRESS ON NANO MECHANICAL

CHARACTERIZATION IN Al2O3 COATING USING RAMAN SPECTROSCOPY

Yoshihisa Tanaka1, Makoto Tanaka

2

1 National Institute for Materials Science (NIMS),

1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan 2 Japan Fine Ceramics Center,

2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587, Japan 1 E-mail: TANAKA.Yoshihisa@nims.go.jp

KEY WORDS: Aerosol deposition method (ADM), Nanoindentation, Residual stress, Raman

piezo-spectroscopy

Environmental barrier coatings (EBCs) are refractory-oxide ceramic coatings applied to the

surfaces of ceramics and metallic parts in the hottest parts such as turbine engines to operate

at significantly higher temperatures under the flow of harsh, high-pressure steam, corrosive

gases and so on. Aerosol deposition method (ADM) is a candidate for nanostructured ceramic

coatings for advanced applications for EBCs [1]. Al2O3 coatings with 250 nm thickness were

fabricated on mullite substrates (Al2O3/Mullites) with different impact velocities of Al2O3

powder by the ADM. The Al2O3/Mullite was heat treated in air at 1573K for 30h. In order to

improve the mechanical characterization of coatings,

the hardness and the modulus of the coatings were

evaluated quantitatively by nanoindentation. The

residual stresses in the coatings were measured by

Raman piezo-spectroscopy using the Cr3+

fluorescence band. The inhomogeneous tensile

residual stress distribution was found in the Al2O3

coating due to the different coefficient of thermal

expansion between the coating and substrate (Figure

1). The effects of residual stress on the nano

mechanical characterization and the process

conditions were discussed.

Reference

[1] Jun Akedo, “Aerosol Deposition of Ceramic Thick Films at Room Temperature:

Densification Mechanism of Ceramic Layers”, J. Am. Ceram. Soc., 89 [6] 1834–1839 (2006).

Figure 1 Residual stress distribution

in Al2O3 coating by ADM.