Eric Baril

Initial evaluation of bone ingrowth into a novel porous titanium coating

Porous metals (sintered beads and meshes) have been used for many years for different orthopedic applications. Metal foams have been recently developed. These foams have the advantage of being more porous than the traditional coatings. Their high porosity provides more space for bone ingrowth and mechanical interlocking and presents more surface for implant-bone contact. The objective of this study was to evaluate in vivo bone ingrowth into Ti implants covered with a novel Ti foam coating. This foam contains 50% in volume of interconnected pores and a higher surface area compared to dense Ti. Both coated implants and dense Ti controls were placed transcortically in the rat tibia. The animals were sacrificed at 2 weeks after implantation, and the amount of bone in the implants was determined using backscattered electron imaging and X-ray microtomography. Already at this time interval, the pores within the Ti foam showed 97.7% bone filling, and the bone-implant contact area was significantly increased compared to dense Ti controls. These initial results indicate that this novel Ti foam is biocompatible, has the capacity to sustain bone formation, and can potentially improve osseointegration.

Interstitial elements in titanium powder metallurgy: sources and control

Abstract The effect of interstitials on the mechanical properties of cast and wrought titanium alloys has been extensively reported but less information is available on the effect of contamination during PM processing. The sources of interstitial contamination when processing titanium powders by compaction, isostatic pressing, powder injection moulding (PIM) and innovative foaming processes are reviewed, focusing specifically on oxygen. The initial powder characteristics (surface area, size), process parameters (time, temperature) and environment (atmosphere, binder, support) may all have significant impact on the final interstitial content. It is, therefore, important to identify and control the sources of contamination by interstitials. A case study on PIM is provided to illustrate the relative contribution of the different sources.

Foam-coated MIM gives new edge to titanium implants

Titaniums characteristics of lightness combined with strength and compatibility with human tissue makes it an ideal metal for medical implants. When manufactured in porous forms, bone integration is encouraged giving long-term stability. Researchers in Canada have been looking at dental implants that have a dense titanium core and a porous foam composite coat…

A MIM Route for Producing Ti6Al4V-TiC Composites

Discontinuous reinforced titanium matrix composites have generated significant interest due to their compelling properties such as their specific strength and wear resistance at room and elevated temperatures. For these reasons, these materials have been considered in various applications such as automotive (valve components), aerospace (engine components) and medical devices (implants). Metal injection molding (MIM) has proven to be an efficient near net-shape technology suitable for high volume manufacturing of parts having complex geometries. The MIM technology is particularly attractive for producing composites as the metallic matrix does not go through the liquid state. This helps minimizing the segregation of the hard particles. MIM also reduces the needs for machining. However, the production of titanium components with the MIM process has its own challenges and limitations, such as presence of porosities and coarser microstructures compared to wrought products. The present work introduces the results obtained during the development of a MIM route for producing Ti6Al4V-5wt%TiC composites. The feedstock developed is wax-based and incorporates a pre-alloyed metal powder. The microstructure, mechanical properties at room and elevated temperatures, the wear resistance and the thermal diffusivity of the composites have been characterised. Properties are compared with those of a Ti6Al4V MIM material produced with the same feedstock and process but without TiC as well as with those of wrought Ti6Al4V reported in the literature. The presence of a small amount of TiC promotes densification and grain size refinement and affects the surface finish of the sintered components. Tensile properties of the composites are comparable or better than those of wrought Ti6Al4V (ASTM F1472). Improved mechanical properties compared to unreinforced material are associated to the higher density, finer grain size as well as solution strengthening of the titanium matrix.

Numerical Simulation of the Flow Through Metallic Foams: Multiscale Modeling and Experimental Validation

In this work the incompressible steady‐state flow through a metallic foam matrix is solved by a finite element method. A multiscale approach combining the solution at the pore level by an immersed boundary method and the macro‐scale solution with simulated permeability is used. The micro scale solution of the flow takes into account the details characterizing the geometry of the foam (μCT scans) and is used to determine the permeability coefficients in the Forchheimer’s model. In a second step, a numerical approach is used to solve the flow at the macro scale by modelling the presence of the foam via a source term corresponding to the pressure drop computed at the micro scale. Such simulation gives the opportunity to solve the flow in complex configurations in which the foam is only a part of the computational domain. The computed pressure drop as a function of the flow rate on the macro scale configuration replicating an experimental set‐up is compared with the experimental data for various foam thicknesses.