Valve seat insert of two layers of same compact density

A method of making a two layer valve seat insert having a valve seat face layer and a base layer, the method comprising 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, characterised in that said valve seat face layer and said valve seat base layer have substantially the same green density after compaction and in that said two layers have substantially equal size change on sintering;said size change on sintering being controlled by a step selected from the group comprising the addition of up to 6 wt % copper to at least one of said powder mixtures;and;the addition of carbon powder in the range from 0.6 to 1.2 wt % to the base layer powder mixture.