Electrochemical infiltration into laser sintered porous graphite and silicon carbide
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Indirect laser sintering is a technique used for direct manufacturing of high melting materials such as graphite and silicon carbide. This technique produces parts with high pore volume fraction and poor structural stability. Such parts are post processed using melt infiltration techniques with metals or alloys such as copper and brass. These processes require high temperature and are not environmentally sustainable and may also encounter restrictions because of infiltration atmosphere. Electrodeposition of a metal into the porous parts produced via laser sintering is an alternate route for filling these parts. Such a route required infiltration of the porous parts with a suitable electrolyte and subsequent electrodeposition of the metal ions into the pore network. Electrodeposition provides a versatile and convenient route to the realization of bulk structures and coatings of metal matrix composites. In the present study, electrodeposition of copper into the pore network of laser sintered graphite and silicon carbide was studied. A theoretical model based on Butler-Volmer equation was made to predict electrodeposition rates across the porous preforms by simulating the current density distribution across the porous part in an electrodeposition cell. The theoretical model was used to determine most favorable conditions required to complete electrolytic infiltration. Electrolytic infiltration of copper was carried out into laser sintered graphite and silicon carbide parts and commercially available porous preforms such as Nomex felt, graphite felt and a stainless steel mesh, using flow electrolysis methods. This study shows that electrochemical deposition of metals in the pore network of a highly porous material is possible under certain conditions. It was realized that the most favorable conditions for electrolytic infiltration exist when the porous preform being infiltrated is thin, and is a poor conductor of electricity. Hence, it is possible to fabricate highly dense metal matrix composite coatings via electrochemical infiltration. In this study Nomex fibers, Stainless Steel 316 mesh, graphite and silicon carbide were used to reinforce electrodeposited copper coatings on copper-110 alloy, and their thermal and tribological properties were measured.