Wetting phenomena for liquid Cu and Cu alloys on Fe-base substrate

Liquid phase sintering is used for the consolidation of powder based materials to enhance densification by the activation of diffusion rates and sintering kinetics. However, an inappropriate interaction between the liquid and the solid powdered skeleton can promote excessive swelling instead of densification, and the purpose of the liquid phase process would not be fulfilled. In the Powder Metallurgy (PM) industry, Cu is among the main alloying elements used in the production of low alloyed sintered steels. Cu promotes the formation of transient liquid below the common sintering temperatures (1120 degrees C). Although it favors rapid homogenization and can be used to effectively transport other alloying elements, it causes a significant swelling effect upon melting that needs to be controlled in order to maintain a proper dimensional stability. The dimensional expansion associated to Cu melting and its distribution in a Fe-base system has been mainly treated in the literature on the basis of dilatometry studies. A systematic study of the influence of different sintering parameters has never been included in that discussion and the information in the literature about the wetting behavior of liquid Cu or Cu alloys is scarce. This work presents an insight into Cu wetting behavior on plain Fe and steel substrates - which is compared to Cu-base a Ni-base liquid formers - using sessile drop experiments. The sensitivity to wetting conditions is addressed by modifying atmosphere conditions (either H-2 containing atmosphere or Ar is used) and interfacial interactions between the liquid and the solid (each liquid former presents a dissolutive condition in contact with Fe, the Cu-based liquid dissolves up to 1.5 wt.% Fe while the Ni-based around 35 wt.%) (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.