Directional solidification mould

Abstract

A mould for use in directionally solidifying a component has a casting cavity including a single crystal selector spiral which is a helical passage having not less than 1¼ and not more than 1½ turns.

1 . A mould for use in directionally solidifying a component, the mould having a casting cavity including a single crystal selector spiral, wherein the selector spiral is a helical passage having not less than 1¼ and not more than 1½ turns. 
   
   
       2 . A mould according to  claim 1 , wherein the component is an aerofoil of a gas turbine engine, the casting cavity further includes a component cavity portion for forming the aerofoil, and the selector spiral and the component cavity portion are in fluid communication, the selector spiral and the component cavity portion being arranged such that the axis of the selector spiral aligns with the stacking axis of the aerofoil when the aerofoil is formed in the component cavity portion. 
   
   
       3 . A mould according to  claim 1 , wherein the mould is adapted to be connectable to a second mould having a second casting cavity for forming the component, the selector spiral and the second casting cavity being in fluid communication when the moulds are thus connected. 
   
   
       4 . A mould according to  claim 1 , wherein the first casting cavity further includes a starter block cavity portion in fluid communication with the selector spiral, the selector spiral and the starter block cavity portion being arranged such that, during directional solidification, growing crystals enter the selector spiral from the starter block cavity portion. 
   
   
       5 . A mould according to  claim 4 , wherein the starter block cavity portion is configured so that, when the selector spiral is positioned above the starter block cavity portion, a part of the starter block cavity portion extends vertically above the entrance to the selector spiral to provide a trap for debris in the cavity. 
   
   
       6 . A mould according to  claim 1 , wherein the mould further has a seed crystal in fluid communication with the selector spiral, the selector spiral and the seed crystal being arranged such that, during directional solidification, the seed crystal grows and enters the selector spiral. 
   
   
       7 . A pattern for use in forming a mould according to  claim 1 , the pattern being formed of material that can be eliminated to form the casting cavity of the mould when the pattern is coated with a material which forms the walls of the mould, and at least a portion of the pattern corresponding to the selector spiral. 
   
   
       8 . A pattern according to  claim 7 , wherein the pattern has a cap portion extending from the part of the pattern corresponding to the entrance to the selector spiral, the cap portion being configured to cap, in use, a seed crystal or a further pattern corresponding to a starter block cavity portion. 
   
   
       9 . A pattern according to  claim 8 , wherein the cap portion is configured so that, when the portion of the pattern corresponding to the selector spiral is positioned above the cap portion, a part of the cap portion extends vertically above the part of the pattern corresponding to the entrance to the selector spiral, whereby said part of the cap portion corresponds to a trap for debris in the cavity of the mould. 
   
   
       10 . A pattern according to  claim 7 , wherein the pattern has an engagement portion which extends from a part of the pattern corresponding to the exit from the selector spiral for a growing crystal, in use, the pattern being joinable to a further pattern having a complementary engagement portion. 
   
   
       11 . The combination of a pattern according to  claim 10  and the further pattern. 
   
   
       12 . A method for directionally solidifying a component with the mould of  claim 1 . 
   
   
       13 . A method for forming a mould with the pattern or patterns of  claim 7 . 
   
   
       14 . A component moulded using the mould of  claim 1  and still attached to material solidified in the single crystal selector spiral.