Gating system for continuous pressure infiltration processes

Abstract

A system of gating orifices for continuous pressure infiltration processes eliminates blow-out of the pressurized molten metal matrix material and friction damage to the infiltrated preform. The system includes three or more orifices along a vertical path of an upwardly moving preform which passes from vacuum or atmospheric pressure into a pressurized infiltrating bath of molten metal, then into a pressurized atmosphere in which the matrix fully solidifies, and from there to an atmospheric environment. The entering orifice, at the bottom of the pressurized bath, is elongated in the direction of the preform movement to provide a temperature gradient from above the matrix material melting temperature at the bath to below the solidification temperature farthest from the bath. The resulting liquid-mushy-solid sequence of the matrix material forms a solidification seal to prevent blow out of the pressurized molten metal. Another elongated orifice(s), at the top of the bath, also has a temperature gradient to control the solidification of the matrix material in the infiltrated preform. This orifice does not function as a pressure seal. An uppermost orifice, not involved in the solidification process, seals against gas losses around the fully solidified composite. By separating the solidification and pressure sealing processes of the exiting orifices, molten metal blow out is prevented and friction-caused problems between the solidification gates and the traveling preform are eliminated.