Internal Stress in EB-PVD Thermal Barrier Coating under Heat Cycle
As the top coating, zirconia with 4 mol% yttria was electron beam-physical vapor deposited (EB-PVD) on the bond coating of CoNiCrAlY. The substrates were rotated during EB-PVD process and the rotation speeds were 5 (R5) and 10 rpm (R10). The thickness of the top coating was 0.12 mm. In order to investigate the change of the internal stress in the top coating under a heat cycle, the specimen was heated from a room temperature to 1293K, the internal stress was measured in-situ by a strain scanning method with hard synchrotron X-rays at each temperature step. For the specimen R5, the internal stress increased from about -100 MPa to about 100 MPa with the increase in temperature, then the stress relaxation of the top coating occurred over 1093K. In the cooling process, the internal stress decreased, however, the changing rate of the internal stress was small as compared with the heating process. This was caused by the feather-like structure sintered. For the specimen R10, the internal stress did not show a tension in the heating process, it was caused by the separation between columnar structures.
T. Chandra, N. Wanderka, W. Reimers , M. Ionescu
K. Suzuki and T. Shobu, "Internal Stress in EB-PVD Thermal Barrier Coating under Heat Cycle", Materials Science Forum, Vols. 638-642, pp. 906-911, 2010