Journal of Materials Research and Technology (Sep 2021)
Analysis of biomedical titanium implant green parts by X-Ray tomography
Abstract
In this study, X-ray tomography was applied as a non-destructive test to investigate the internal defects of the green part produced with Powder injection molding (PIM). PIM is a material processing technology that combines injection molding with powder metallurgy. The determination of multiple parameters such as rheology, molding, bonding, and sintering stages in the PIM method requires a long time, energy, and high cost. Metal and ceramic injection molded parts are known to be susceptible to defects like cracks, weld lines, bubbles, or gaps. The examination and elimination of these defects are critical to the safety of the products because even a very short crack can significantly reduce the tensile and fracture strength of the parts. The internal structure analysis of the green parts after molding is very difficult. Defects (internal cracks, micropores, jetting, etc.) occurring in the green part will occur in the sintered. Therefore, it is essential to analyze the possible defects on molded parts before applying the ongoing process to save time and costs. Since the medical implants are in complex shape in general, the more internal defects can be seen at molding stage, it is needed to check the internal structure without any destruction, because there is no chance toleave them for recycle in the case of any defect. In experimental studies, it was observed that there were defects of edge, interior, and gaps in X-ray analysis for four different injection parameters. In X-ray analysis, the defects free parts were obtained for green part 4 parameters (temperature of 237 °C, flow rate of 20.11 cm3/s and pressure of 120 MPa). As a result of X-ray analysis, the difference between green part 1 and green part 4 is clearly visible in terms of defect. Injection temperatures, speeds and pressure play important role on originating of defects.
