Thermal cycling behavior of EB-PVD NiAlHf coating via laser shock peening treatment

Abstract

NiAlHf coatings prepared via the electron beam physical vapor deposition (EB-PVD) technique were modified using the laser shock peening (LSP) technique. The surface states and microstructures, including phase composition, crystal defects, and reactive element distribution, were characterized and analyzed. The coatings were subjected to 1200 °C for 100 thermal cycles. The high-temperature service performance of the coatings was evaluated by comparing the growth behavior of the thermally grown oxide (TGO) and the coating peeling. The results showed that after 100 thermal cycles, the samples without LSP treatment exhibited oxide film damage and large-area internal oxidation, nearly resulting in coating failure. In contrast, the samples treated by LSP demonstrated intact oxide films and strong antioxidant properties. The modified coating surface is flat, high-density dislocation is introduced, and the coating grain is refined, providing more diffusion channels for the selective oxidation of Al elements. This refinement of the grain structure provides a prerequisite for the uniform growth of thermal TGO and significantly reduced TGO spallation. In addition, the influence of the reactive elements in the substrate on the growth behavior of TGO was necessary to be considered. LSP is a promising technology for improving the thermal cycling performance of NiAlHf coatings.