Thermal Cycle Properties of Plasma Sprayed Oxidation-Resistant Metallic Coatings
Thermal cycle resistance of Ni-20Cr, Ni-50Cr and CoNiCrAlY coatings produced by air plasma spraying was investigated according to Japanese Industrial Standard Testing method for thermal cycle resistance of oxidation resistant metallic coatings (JIS H 8452: 2008). The specimens were exposed to a cyclic heating and cooling regimen comprised of up to 100 cycles of 10 hours heating to 1000 °C or 1093 °C in air followed by cooling. The thermal cycle resistance of oxidation-resistant metallic coatings was found to depend strongly on testing temperature and on the chemical composition of the coating materials. In thermal cycle testing at 1000 °C, no remarkable failure was observed in any specimen. However, in thermal cycle testing at 1093 °C, spalling was observed over the entire surface of the Ni-20Cr coating, although the Ni-50Cr and the CoNiCrAlY coatings exhibited excellent thermal cycle resistance even upon exposure to 100 thermal cycles. The CoNiCrAlY coating showed mass gain with increasing number of thermal cycles due to preferential oxidation between thermal spray particle splats. Furthermore, the failure behavior of specimens was investigated in detail by SEM, XRD, EPMA, etc.
Toshio Maruyama, Masayuki Yoshiba, Kazuya Kurokawa, Yuuzou Kawahara and Nobuo Otsuka
S. Takahashi et al., "Thermal Cycle Properties of Plasma Sprayed Oxidation-Resistant Metallic Coatings", Materials Science Forum, Vol. 696, pp. 296-301, 2011