Homogeneous Metal Parts by Infiltration 69
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Infiltration of powdered metal parts made by SFF processes enables densification with negligible dimensional change, but typically uses a dissimilar infiltrant material resulting in poor corrosion resistance, machinability, and a heterogeneous composition inconducive to certification for critical applications. A new approach called transient liquid-phase infiltration is described using an infiltrant composition similar to that of the powder skeleton, but containing a melting point depressant. Upon infiltration, the liquid undergoes diffusional solidification at infiltration temperature and eventually the composition becomes homogeneous. Parts over 20 cm tall have been fabricated through careful selection of skeleton and infiltrant compositions, skeleton powder size, and infiltration technique. The work presented in this paper uses a nickelsilicon alloy to infiltrate a skeleton of pure nickel powder.