Abstract
The influence of the particle velocity on the formation intermetallic of coatings is discussed. The primary phases of detonation sprayed NiAl coatings are NiAl and Ni3Al, and also a solid solution of Ni in NiAl. The lamellar and homogeneous distribution of Al may be due to the oxidation of the powder particles during their flight in the pulsating high temperature, high velocity jet of the gas detonation process. During heating and melting of the powder particles, an aluminum oxide film is formed. This film takes part in the coating formation and affects the Al distribution. Another important observation is the presence of NiAl and Ni3Al phases in the coating structure. The transition zone between the coating and substrate has a thickness of 10-15 µm. The character of the distribution curves of Al and Ni confirms the lamellar distribution of NiAl and Ni3Al phases in the coating.
