Experiencias en la fabricación de titanio con gradiente de porosidad mediante técnicas de pulvimetalurgia

Abstract

Titanium is recognized as the best biometal for applications in bone implant.However it presents some difficulties as is the mismatch between its modulus of elasticity(stiffness) and that of the bone that replace. This difference produce stress-shielding, aphenomenon by which bone is retracted, weakens and can suffer a new fracture. One possiblesolution is to decrease the stiffness by obtaining a porous structure with controlled porosity innumber, size and shape of the pores. The presence of different tissues in contact with theimplant makes ideal to have a titanium metal structure with porosity gradients. A suitabletechnique for obtaining this structure is powder metallurgy (PM). This paper use PMtechniques with TiH2 as the titanium source and ammonium bicarbonate as pore spacerparticles, sintered at 1000 ° C in argon atmosphere. There were obtained samples withlongitudinal and radial porosity gradient. The main drawbacks are found in matrix fillingtechniques for compact the greens. This causes joints between layers with different porositynot adequate and separated by differential shrinkage during the sintering treatment. Despitethis, optimization of the treatment conditions enables the samples obtained present very goodadhesion between layers.