| 摘要 |
A valve seat made by compacting and sintering a water atomised vacuum annealed high alloy powder which comprises (by weight): 15-30% Cr, 0.5-5% Mo, 1-2% C, optionally one or more other alloying elements, with the balance being Fe. (Claim 15 species an alloy which comprises 0.5-5 % of at least one of Mo, V, W and Nb). The valve seat comprises at least 10 % of this powder and it may be completely formed therefrom (allowing up to 2 % for additives). Other powders which may be mixed with the above powder are: iron powder, low alloy steel powder, machinability aids, solid lubricants, sintering enhancers, and/or hard particles to a level of 30 % or less of the total powder mixture. Processing can involve cryogenic treatement followed by tempering to form a martensitic matrix with carbides distributed therein. |
