| 摘要 |
<p>A composite casting is made by placing a solid metal insert in a mould and casting molten metal round the free sections of the insert. Prior to insertion, the free sections are coated with an alloy contg. boron. The alloy has a lower m.pt. than both metals, and has the same principal constituent as >=1 of the metals. After solidification of the casting, heat treatment is used so the boron diffuses into both metals. The insert pref. has anisotropic metallurgical properties obtd. using oriented grains or directional solidification producing a columnar structure. The insert may alternatively have a directionally solidified structure with a eutectic compsn.; or be a metal matrix reinforced by fibres. The insert pref. has the shape of a wing or blade and may be made of a Ni- or Co- base superalloy. The B-contg. alloy pref. has the compsn. 5-25% Cr, 1-4% B, 0.05-0.2% C, rest ni; and the heat treatment is pref. at 1010-1230 degrees C. Esp. used for mfr. of components for gas turbines, e.g. blades, where the blade forms the mould insert and has anisotropic properties.</p> |
