Titanium and titanium-nickel parts processed by PIM of TiH2-based feedstocks

Titanium and Titanium-Nickel parts have been processed from titanium hydride and blends of titanium hydride and elementary nickel powders respectively. PIM feedstocks were processed in sigma blade mixers by using binders composed of low density polyethylene, paraffin wax and stearic acid. A two-step debinding process has been used, which consists of solvent debinding in heptane at 50°C (122°F) followed by thermal debinding in a MIM furnace at 500°C (932°F) under argon atmosphere. Dehydrogenation of TiH2 powder is performed simultaneously with thermal debinding. Titanium parts were sintered at 1200°C (2192°F) under argon. The mechanical properties of sintered parts were measured by tensile tests. The microstructure was characterized by optical metallography and scanning electron microscopy. Special care in powder handling, feedstock preparation, debinding and sintering atmospheres, allowed to obtain low residual oxygen, nitrogen and carbon contents, which were determined by quantitative analysis. Watch bracelet segments were injection moulded as test parts, showing good shape preservation and reproducibility. Titanium-nickel shape memory alloys were sintered at 1200°C (2192°F) under hydrogen. Differential scanning calorimetry revealed the presence of a reversible martensitic transformation above room temperature. Shape memory effects of more than 4% have been measured.