Influence of TiH2 addition on the microstructure and mechanical properties of spark plasma sintered TiCx-NiTi/Ni3Ti cermets

• Fully densified TiCx–NiTi/Ni3Ti cermets were prepared by spark plasma sintering.
• TiH2 powder was added to modify the C/Ti ratio (x) and overall binder composition.
• NiTi was obtained when x was 0.7, while Ni3Ti was generated when x was 0.8 or 0.9.
• The NiTi binder cermet was markedly tougher than the Ni3Ti binder cermets.
• The cermet hardness increased with increasing x and decreasing binder content.

TiC0.7-10.7 vol% NiTi, TiC0.8-7 vol% Ni3Ti and TiC0.9-8 vol% Ni3Ti cermets were prepared by spark plasma sintering. The C/Ti atomic ratio of the TiC phase and overall binder composition was modified by adding TiH2 powder into the TiC0.95 + Ni49.4Ti50.6 starting powder mixture. The Ti loss from the NiTi starting powder during sintering, converting the metal binder from NiTi into Ni3Ti, could be avoided by the addition of TiH2 with a concomitant change of the TiCx phase stoichiometry. A ductile NiTi binder was obtained in combination with a TiC0.7 phase, while a more brittle Ni3Ti binder was generated in combination with TiC0.8 or TiC0.9. The hardness of the cermets increased with increasing C/Ti ratio of the TiCx phase and decreasing NiTi or Ni3Ti content, whereas the bending strength and fracture toughness of the NiTi binder cermet was significantly higher than for the Ni3Ti binder cermets. The E-modulus of the NiTi binder cermet was substantially lower than for the Ni3Ti binder cermets.