Mould for casting a monocrystalline component

A method for casting a component in a directional solidification casting process having a preferred direction of dendritic growth <001> which is inclined to a direction Y of a thermal gradient, comprising;

• providing a mould having a shell defining a cavity for receiving molten material, the cavity defining a three dimensional shape made up of a finished component geometry portion and a sacrificial geometry portion, wherein the sacrificial geometry portion includes a notch which is shaped and positioned so as to, in use, contain dendritic growth in an axial direction <001>, different from the off-axial primary <001>, within the sacrificial geometry portion (45) of a casting solidifying in the mould,
• introducing into the sacrificial geometry portion a seed crystal having a dominant growth direction of <001>,
• arranging the mould in a thermal gradient, the coolest end of the gradient being adjacent the sacrificial geometry portion,
• introducing molten material into the mould and gradually withdrawing the mould in a direction towards the coolest end whereby to control solidification of the material.