Sinterbonding cobalt-cemented tungsten carbide to tungsten heavy alloys

摘要

Cobalt-cemented tungsten carbide (WC-Co) powder was sinterbonded to nickel-iron tungsten heavy alloy (WHA) for use in high-temperature tooling applications. Sinterbonding was performed under various conditions, including changes to the sintering conditions and initial WHA material forms, to determine various processing conditions that yield a consolidated interface indicative of a high degree of bonding. Sinterbonding WC-Co to fully dense WHA bar stock yielded a consolidated interface comprised primarily of complex r|-carbides. Defects at the interface, including voids, microcracking, and porosity were the result of.other sinterbonding processing conditions explored in this work. Co-rich eta-carbides were found to form at the interface in every condition examined. A thermodynamic evaluation of eta-car-bides as a function of carbon activity determined that Co-rich r|-carbides formed preferentially in regions of low carbon activity. The predicted thermodynamic trends are in agreement with interfacial micro-structural observations.