Residual Stress in Zirconia Coating by EB-PVD Method

Abstract

The Ni-based superalloy IN738LC was used as the substrate material, and CoNiCrAlY powder was pressureless plasma-sprayed on the substrate as the bond coating. Zirconia was coated as the top coating by the electron beam-physical vapor deposition (EB-PVD) method. In the EB-PVD process, the specimens were kept at 1223K and rotated with 5rpm, 10rpm and 20rpm. According to the microscopic observation and the result of the pole figures, the top coatings had a columnar structure, which was made by the piling up of (111) planes. The cross section of the column had a diamond shape, and its diagonal was parallel to the rotation axis. The residual stress on the surface of the top coatings was evaluated by the X-ray diffraction method. Each diffraction profile was separated into the 133 and the 331peak, and the residual stress was measured by the sin2ψ method. The measured residual stresses were –76.7MPa for 5rpm, –63.0MPa for 10rpm and –25.1MPa for 20rpm.