Effect of Aluminum Content on Microstructure and Properties of Nickel Aluminum Alloy Coating Prepared by Atmospheric Plasma Spraying

With Ni5Al aluminum-coated nickel alloy powder and mixtures of pure aluminum and Ni5Al aluminum-coated nickel alloy powder with aluminum mass fraction of 10% and 20% as raw materials, Ni5Al, Ni10Al and Ni20Al alloy coatings were prepared by atmospheric plasma spraying technology on the surface of GH4169 nickel-based superalloy. The effects of aluminum content on the phase composition, microstructure, mechanical properties, and electrochemical properties of the nickel aluminum alloy coatings were studied. The results show that the alloy coatings with different aluminum content were mainly composed of nickel solid solution, accompanied by the formation of NiAl and NiAl₃ phases. With the increase of aluminum content, the number of diffraction peaks of NiAl₃ and NiAl phases increased, and the intensity of diffraction peaks of nickel solid solution phase decreased. Al₂O₃ phase was present in both Ni10Al and Ni20Al alloy coatings, and Ni₃Al phase was present in Ni5Al alloy coating. With the increase of aluminum content, the oxides in the alloy coatings decreased, the microhardness and bonding strength of the coating increased, and self-corrosion current density decreased, indicating improved corrosion resistance. There were a large number of cleavage planes and cleavage steps in the nickel aluminum alloy coating fracture, and the fracture mode was mainly brittle fracture. The Ni5Al alloy coating fracture also had a "rock sugar" shape, and the Ni10Al alloy coating fracture also had a small number of dimples.