The chemical elements used in the binder system for the injection moulding of titanium metal powders will change the final composition when not adequately controlled. Excess levels of carbon, hydrogen, nitrogen and oxygen adversly effect the mechanical properties by embrittlement. Before sintering debinding is done to remove the maximum possible amount binder thereby ensuring residual carbon levels are minimal. Testing the mechanical properties of samples can acknowledge deficiencies in the final part however, identification of the nature of the deficiencies is not so simple.In this work titanium-based metal parts were made using the metal injection moulding process and the microstructure was inspected. The investigation used scanning electron microscopy imaging, electron dispersion spectroscopy point and area mapping, LECO trace analysis and X-ray diffraction elemental mapping. Following this samples were ground and polished before immersing their surfaces in an etching solution to further expose the microstructure. Although the data collected from debinding indicated the binder had been removed prior to sintering contamination was still evident. This result showed that the traditional means of reporting binder levels in proportion to part mass after debinding is inaccurate. Subsequently laser induced breakdown spectroscopy was trialed as a method by which to determine the binder levels for parts in the green, grey, brown and sintered form.Interstitial carbon is a known alpha stabiliser however excess carbon on particle surfaces may impinge on particle coalesence limiting density levels. Comparison of the part mass method of binder determination with the laser induced breakdown spectroscopy results showed that the mass determination method was more accurate for the green and grey parts but the laser induced breakdown spectroscopy results were able to detect the residual binder more accurately for brown and sintered parts.

This work investigates the debinding process of powder compacts formed by metal injection moulding (MIM) of feedstocks comprised of HDH Ti or HDH Ti-6Al-4V powder mixed with a binder of a predetermined ratio of water soluble polyethylene and wax. The full debinding process has three stages: a solvent debinding process to leach the water soluble component, a drying phase allowing the removal rate to be measured and a thermal treatment step for removing the wax components, leaving the backbone components to retain part geometry prior to sintering. Leaching of the water soluble component was monitored and the results were consistent with the general correlation which predicts that binder removal time increases by a factor of 4 when the section thickness is doubled. Uniformity of binder removal, defect formation and particle surface degradation in Ti MIM parts are also discussed.

Titanium metal injection molding allows creation of complex metal parts that are lightweight and biocompatible with reduced cost in comparison with machining titanium. Laser-induced breakdown spectroscopy (LIBS) can be used to create plasma on the surface of a sample to analyze its elemental composition. Repetitive ablation on the same site has been shown to create differences from the original sample. This study investigates the potential of LIBS for selective surface sintering of injection-molded titanium metal. The temperature created throughout the LIBS process on the surface of the injection-molded titanium is high enough to fuse together the titanium particles. Using the ratio of the Ti II 282.81 nm and the C I 247.86 nm lines, the effectiveness of repetitive plasma formation to produce sintering can be monitored during the process. Energy-dispersive X-ray spectroscopy on the ablation craters confirms sintering through the reduction in carbon from 20.29 Wt.% to 2.13 Wt.%. Scanning electron microscope images confirm sintering. A conventional LIBS system, with a fixed distance, investigated laser parameters on injection-molded and injection-sintered titanium. To prove the feasibility of using this technique on a production line, a second LIBS system, with an autofocus and 3-axis translation stage, successfully sintered a sample with a nonplanar surface.

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In this study, a structural hold down component was designed and produced using the particulate injection moulding (PIM) process. The material of choice was titanium due not only to the material properties but also due to the desire to create custom-made components for a state-of-the-art marine vessel, Earthrace 2.On removal from the mould, the green parts were seen to have an irregular surface on the top face. Known as surface bloom, it can be seen during moulding of single-phase commodity polymers as a result of changes in the polymer density, due to shear stresses and irregularities of turbulent flow.Literature suggests the surface bloom is a result of a separation between the two phases, but the preliminary findings show little evidence of this within the sectioned profile. The sintered parts were sectioned, and inspection of the surfaces was done using metallographic techniques. The use of CAD models enabled the defect to be modelled and the models provided a more likely scenario. It was further confirmed that there were no through part defects present and although the surface irregularities were caused by separation of the two-phases, the effect was restricted to the outer surface of the parts.