he use of EBM (Electron Beam Melting) for the production of objects and components with complex shape has strongly increased in the past years in different industrial sectors. For the biomedical sector, in particular, the use of EBM allows to obtain bio compatible metallic cellular solids that may strongly enhance the osseointegration of orthopaedic implants, while keeping good mechanical properties. In this work, two different cellular solids obtained by EBM processes of commercially pure grade 2 titanium have been characterized. The investigated structures, having a complex three dimensional foam shape, cannot be easily obtained using conventional productive technologies. For this work, two different kinds of structure have been produced: (A) with a smaller single cell diameter and (B) with a larger single cell diameter. These structures have been completely characterized and confronted with literature results for commercially pure titanium and Ti-6Al-4V grade 5. The relative density has been evaluated using two different techniques, with scale and caliber and with Archimede's method, the single porosity diameter has been evaluated using Scanning Electron Microscope Images and image post-processing software, the composition has been investigated by X-ray spectroscopy using the EDXS (Energy Dispersive X-ray Diffraction) equipment of the SEM, the microstructure and the grain dimension has been investigated on polished samples using chemical etching performed with Kroll solution (2% HF, 6% HNO3 in demineralized water) and the mechanical properties have been evaluated using a UMTS equipment. Mean porosity resulted to be close to spongy bone (near 77% for sample A and near 89% for sample B). The mean porosity diameter (0.76 mm for sample A and 1.37 mm for sample B) resulted to be sufficient to enhance the osseointegration of the component, in particular in sample A. Vickers microhardness resulted to be around 300 HV for both samples, homogeneous across the entire structure and sensibly higher than literature values for grade 2 titanium (200 HV), while metallographic attack showed a complex microstructure with irregular shaped grains characterized by a high surface over volume ratio and compenetration between the different grains. Mechanical tests showed that sample A, as expected, is more resistant than sample B (Tensile ultimate strength: 15.5 MPa for sample A and 5.3 for sample B, compressive ultimate strength 13 MPa for sample A), while sample B showed a lower elastic modulus, even lower than literature data on spongy bone. This study results suggest that the two different structures in grade 2 titanium may be successfully used for biomedical applications in order to promote osseointegration of prosthetic implants.
Caratterizzazione strutturale e meccanica di biomateriali altamente porosi in titanioc ommercialmente puro per l'ortopedia artroprotesica: Il trabecular titaniumtm
MARIN, Elia;LANZUTTI, Alex;FEDRIZZI, Lorenzo
2011-01-01
Abstract
he use of EBM (Electron Beam Melting) for the production of objects and components with complex shape has strongly increased in the past years in different industrial sectors. For the biomedical sector, in particular, the use of EBM allows to obtain bio compatible metallic cellular solids that may strongly enhance the osseointegration of orthopaedic implants, while keeping good mechanical properties. In this work, two different cellular solids obtained by EBM processes of commercially pure grade 2 titanium have been characterized. The investigated structures, having a complex three dimensional foam shape, cannot be easily obtained using conventional productive technologies. For this work, two different kinds of structure have been produced: (A) with a smaller single cell diameter and (B) with a larger single cell diameter. These structures have been completely characterized and confronted with literature results for commercially pure titanium and Ti-6Al-4V grade 5. The relative density has been evaluated using two different techniques, with scale and caliber and with Archimede's method, the single porosity diameter has been evaluated using Scanning Electron Microscope Images and image post-processing software, the composition has been investigated by X-ray spectroscopy using the EDXS (Energy Dispersive X-ray Diffraction) equipment of the SEM, the microstructure and the grain dimension has been investigated on polished samples using chemical etching performed with Kroll solution (2% HF, 6% HNO3 in demineralized water) and the mechanical properties have been evaluated using a UMTS equipment. Mean porosity resulted to be close to spongy bone (near 77% for sample A and near 89% for sample B). The mean porosity diameter (0.76 mm for sample A and 1.37 mm for sample B) resulted to be sufficient to enhance the osseointegration of the component, in particular in sample A. Vickers microhardness resulted to be around 300 HV for both samples, homogeneous across the entire structure and sensibly higher than literature values for grade 2 titanium (200 HV), while metallographic attack showed a complex microstructure with irregular shaped grains characterized by a high surface over volume ratio and compenetration between the different grains. Mechanical tests showed that sample A, as expected, is more resistant than sample B (Tensile ultimate strength: 15.5 MPa for sample A and 5.3 for sample B, compressive ultimate strength 13 MPa for sample A), while sample B showed a lower elastic modulus, even lower than literature data on spongy bone. This study results suggest that the two different structures in grade 2 titanium may be successfully used for biomedical applications in order to promote osseointegration of prosthetic implants.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
