J. Karthikeyan, ASB Industries, Inc, Barberton, OH; J. Haynes, Pratt & Whitney Rocketdyne, West Palm Beach, FL; A. Pande, Pratt & Whitney Space Propulsion, West Palm Beach, FL

Summary:

Discontinuously reinforced aluminum (DRA) has gained considerable attention in the past due to its attractive mechanical and physical properties. Aluminum alloys such as 6061 have been modified through the addition of discrete hard particles such as SiC and B₄C to add strength and stiffness for improved performance in certain applications. Traditionally, these particles are introduced in melt additions and extruded or made into preforms and cast. Also, these ceramic particles are added in aluminum through a powder metallurgy process resulting in extrusion or forging. In casting, it is difficult to achieve acceptable properties due to inhomogeneous distribution of these particles and also difficulty in making performs for high volume fraction materials. In the powder metallurgy approach, while wrought properties can be achieved, it is difficult to produce isotropic properties due to the extrusion directionality. Thermal spray processing of DRA material has been performed successfully, but still has the disadvantage of melting and re-solidifying the aluminum matrix material as well as reacting with potential substrates such as copper.

In this paper, cold gas dynamic spraying of DRA materials including 6061/B₄C will be discussed. A systematic study on various issues, including the DRA powder preparation, raw material and feedstock characteristics, spray processing technique as well as properties of the spray produced DRA coatings and freeforms was carried out. Wet blending and subsequent drying yielded the required spray feedstock. Optimization of the spray parameters resulted in strong, dense and well bonded coatings with acceptable deposition efficiency and deposition rate values. Characterization of the sprayed coatings showed that these specimens have acceptable characteristics for intended applications. This study have shown that this solid-state spray process can effectively produce desired coatings with high volume fractions of B4C within a fully dense 6061 matrix, with very uniform distribution of carbide particles.