Abstract

In an emerging thermal spray process a coating is formed by exposing a metallic or dielectric substrate to a high-velocity jet of solid-phase particles, which have been accelerated by a supersonic gas jet at a temperature much lower than the melting or softening temperature of the particle material. This is known as "Cold Gas-Dynamic Spray" (CGDS) method. Using this method, 2618 Al substrates were coated with nickel-aluminum bronze powders (~100 and ~400 mesh) in an effort to obtain improved wear resistance. The coatings have been examined for their microstructure, hardness, and bond strength. Triple lug shear tests performed on coated panels provided quantitative measurement of the coating/substrate interfacial shear strength. The steady state wear rates were determined using the pin-on-rotating ring test at a pressure of 690 kPa and a sliding velocity of 9 m/s. The wear resistance of the nickel-aluminum bronze coatings is discussed in conjunction with scanning electron microscopy (SEM) examination of the wear tracks and metallography of the polished transverse cross-sections. Though the coatings are not completely free from porosity, they exhibit high interfacial shear strength and wear resistance due to the low-temperature, ballistic impingement of the powders in the cold gas-dynamic spray method. The ~400 mesh powder coating shows higher interfacial shear strength and wear resistance in comparison with the ~100 mesh powder coating.

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