446 JOINING of WC-Co to Ni by DIRECT DIFFUSION BONDING and USING A Cu-Zn ALLOY

Friday, November 6, 2009: 4:20 PM
Pancho Villa (Camino Real Hotel)
Jose Lemus-Ruiz Sr., Full time professor , Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, 58000, Mexico
Egberto Bedolla-Becerril , Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, 58000, Mexico
Leonel Ceja-Cardenas , Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, 58000, Mexico
Ana Lizeth Salas-Villaseņor , Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, 58000, Mexico
The objective of this work was to study various aspects of liquid and solid state diffusion bonding of cylindrical samples of WC (with 6% Co) and commercially pure nickel (99.5%) produced by direct bonding and brazing using a 25 µm thick 70Cu-30Zn (wt%) alloy as joining element. Joining experiments were carried out on WC/Ni and WC/Cu-Zn/Ni combinations at temperature of 980°C and 1100°C using different holding times in argon (Ar) atmosphere. The results showed that joining occurred by the formation of a homogeneous diffusion zone with no several interfacial cracking and porosity. Scanning electron microscopy (SEM) micrographs show the different intermediate layers formed in the reaction zone, and the width of these layers increases with bonding temperature and time. Electron probe microanalysis (EPMA) revealed that at any particular bonding temperature, Co travel into the Ni side, whereas Ni travel comparatively larger distances in the WC side. Joining strength was obtained by four-point bending testing with a maximum joint strength of 255 MPa for WC/Cu-Zn/Ni samples joined at 980°C and 15 minutes  However high strength joints were obtained over 15 minutes (>100 MPa). On the other hand, four-point bending testing gave a maximum average joint strength higher than 300 MPa for WC/Ni samples joined at 980°C.