Abstract
In order to investigate the phase relationship during the sintering process of TiN–Ni mixed powder compacts, the nickel-rich portion of the vertical section between nickel-solid solution and titanium nitride was studied by using both sintered and arc-melted alloy specimens prepared from Ni and TiN, where a quasi-binary eutectic was found between a nickel-solid solution and stoichiometric TiN in the vertical plane. The eutectic composition was determined to be about 10 wt% Ti and 1.6 wt% N, and the melting point of the eutectic was found to be 1626±4 K. The maximum solubilities of Ti and N in the nickel-solid solution and the nickel solubility in the TiN phase at 1626 K were 4.84 wt% Ti, 0.06 wt% N and 0.31 wt% Ni, respectively.
The structure of a quasi-binary eutectic between nickel-solid solution and TiN showed a complex stripe-like structure.
It was found that nitrogen gas liberated upon formation of nickel-solid solution, but not from the liquid phase during the sintering process of TiN–Ni mixed powder compacts. Judging from the sintered densities, the liquid phase sintering of the TiN–Ni mixed powder compacts may be disturbed by liberated nitrogen gas which increases from about 1073 K to the eutectic temperature.
