Influence of TiH2 addition on the microstructure and mechanical properties of spark plasma sintered TiCx NiTi/Ni3Ti cermets
Abstract TiC 0.7 10.7 vol% NiTi, TiC 0.8 7 vol% Ni 3 Ti and TiC 0.9 8 vol% Ni 3 Ti cermets were prepared by spark plasma sintering. The C/Ti atomic ratio of the TiC phase and overall binder composition was modified by adding TiH 2 powder into the TiC 0.95 Ni 49.4 Ti 50.6 starting powder mixture. The Ti loss from the NiTi starting powder during sintering, converting the metal binder from NiTi into Ni 3 Ti, could be avoided by the addition of TiH 2 with a concomitant change of the TiC x phase stoichiometry. A ductile NiTi binder was obtained in combination with a TiC 0.7 phase, while a more brittle Ni 3 Ti binder was generated in combination with TiC 0.8 or TiC 0.9 The hardness of the cermets increased with increasing C/Ti ratio of the TiC x phase and decreasing NiTi or Ni 3 Ti content, whereas the bending strength and fracture toughness of the NiTi binder cermet was significantly higher than for the Ni 3 Ti binder cermets. The E modulus of the NiTi binder cermet was substantially lower than for the Ni 3 Ti binder cermets.