Effect of nano mold coatings on internal defects of thin wall aluminum alloy gravity castings

In gravity casting of aluminum alloys, turbulent mold filling, reactions between the molten metal and molding materials, melt cooling rate and fluidity as well as inadequate feeding to compensate the solidification shrinkage cause different types of defects. Volumetric defects are among the most important problems in the casting processes and include gas and shrinkage defects which are formed during solidification of the melt. These defects strongly reduce the quality of thin wall castings and have adverse effects on their mechanical properties. In this study, the influence of using nano-ceramics mold coating on sand molds on these defects was investigated and the defects formed in thin samples cast using nano-ceramic mold coating, micro-ceramic mold coating, graphite mold coating and sand mold without coating were compared using x-ray radiography method. The results could lead to production of higher quality AL4-1 alloy components using nano-ceramic coatings.