| 摘要 |
PCT No. PCT/GB94/01044 Sec. 371 Date Jun. 12, 1996 Sec. 102(e) Date Jun. 12, 1996 PCT Filed May 16, 1994 PCT Pub. No. WO94/27767 PCT Pub. Date Dec. 8, 1994A two layer valve seat insert and a method for its manufacture is described. The method comprises the steps of preparing two powder mixtures; a first powder mixture for forming the valve seat face layer; a second powder mixture for forming the valve seat base layer; sequentially introducing a predetermined quantity of each of said first and said second powder mixtures into a powder compacting die and having an interface therebetween substantially perpendicular to the axis of said die; simultaneously compacting said first and said second powder mixtures to form a green compact having two layers and sintering said green compact, wherein at least one of the chemical composition or the physical characteristics of at least one of said first and said second powder mixtures is adjusted so as to result in said valve seat face layer and said valve seat base layer having substantially the same density after compaction. |
