Application of sodium chloride as space holder for powder injection molding of alloy Titanium–Hydroxyapatite composites

Abstract

The development of porous metal structures, especially for the use of titanium alloys in bone implant applications, has attracted the attention of researchers. However, forming porous structures in titanium composites via powder injection molding (PIM) remains in the early stages of analysis, allowing the determination of processing parameters to be studied in greater detail. In this study, the critical PIM parameters for processing porous alloy titanium–hydroxyapatite composites were identified via the space holder method. Titanium alloy (Ti6Al4V) was mixed with hydroxyapatite (HA) at a weight percentage ratio of 9:1 with 20 wt.% sodium chloride (NaCl) as the space holder. Feedstock was prepared by combining the powder with a binder system. Pseudoplastic flow activity, which was the desired rheological property needed for PIM, in the feedstock was determined. A tensile bar specimen was successfully injected with a green strength of 2.92 MPa. The space holder was then removed via water leaching, whereas the binders were removed by a debinding step before being sintered in a high-vacuum condition for 3 h at 1350 °C. The sintered parts were interconnected and had a porosity level of 37.03%. Energy dispersive X-ray mapping revealed that the porous titanium–hydroxyapatite composite contained titanium (Ti), calcium (Ca), phosphorus (P), and oxygen (O) components. This study indicated that the combination of PIM and the space holder method is a promising technique for manufacturing near net-shaped porous titanium–hydroxyapatite composites.