Effect of metallic coatings on infiltration of AK12 alloy into porous carbon graphite frame under non-autoclave impregnation conditions

Abstract

The effect of copper and nickel coatings applied on the carbon graphite framework, as well as on the surface of the open pores of carbon graphite before impregnation by AK12 alloy, in order to obtain composite material carbon graphite—aluminum by non-autoclave technology is studied. It is shown that copper and nickel coatings increase filling of open pores by matrix alloy, which is indicated by increase of physical and mechanical properties and density of composite material after impregnation. It is found that the use of nickel electrochemical coating during impregnation resulted in the formation of a transition zone enriched by nickel at the interface, its concentration sharply decreasing from the periphery to the centre of the pore. When using copper coating, the copper concentration decreases away from the interface, but is traceable across the entire filled cross-sectional area of the metal in the pore, which can be explained by the different diffusion rates of copper and nickel into aluminium. It is shown that the compression strength of specimens with copper coating increased by 17, 92 and 1 10 % at impregnation temperatures of 700, 750 and 850 °C, and of specimens with nickel coating by 14, 75 and 98 % relative to uncoated carbon graphite AG-1500, which is caused by an increase in the metal component in the composition of the composite material.