Thermal barrier coatings (TBC) applied to turbine blades in a jet engine or a gas turbine face a threat of a high-velocity impingement of various foreign objects, which induces serious damage with delamination of TBC. In this study, in order to understand the delamination mechanism of TBC under actual operation conditions, a high-velocity impingement test system under a high temperature condition was developed. In this system, a spherical impactor with a diameter of 1 to 8 mm can be impinged onto a TBC specimen at various temperature up to 900℃. The high-velocity impingement test was conducted to atmospheric plasma sprayed TBC specimens with 8wt.%YSZ topcoat (TC) under room temperature (R.T.) and 900℃ conditions. As a result, a hemispherical indentation was formed at 900℃, which indicates the plastic deformation of TC, in contrast to the brittle deformation observed at R.T.. In addition, vertical and interfacial cracks were formed at both R.T. and 900℃. The cross-sectional observation revealed that the formation process of the interfacial crack at 900℃ was different from that at R.T.. In particular, the interfacial crack tended to become significantly longer at more than 170 m/s at 900℃.

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In order to clarify the corrosion mechanism of corrosion protective thermal sprayed coatings from the viewpoint of corrosion potential measurement, immersion tests and electrochemical measurements were carried out by depositing the thermal sprayed powders on iron substrates in aqueous Na₂SO₄ solutions. Consequently, the corrosion mass loss of the iron base material when the powders were deposited, became smaller than that of the iron base material without powder deposition, and the corrosion of iron was completely suppressed in Al-5mass%Mg and Zn-15mass%Al powders. The change of corrosion potential with time could be fractionated into Al holding the same potential as Fe, Zn-15mass%Al or Mg holding a lower potential than Fe, and Al-5mass%Mg keeping a more noble potential than Fe. The corrosion protective function of these sprayed powders has a greater effect as a barrier layer to suppress the diffusion of dissolved oxygen than a galvanic couple with an iron base material.

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