Eduardo T. Galvani

Ti-13Nb-13Zr Foams for Surgical Implants

The use of titanium and its alloy as biomaterial is increasing due to their low modulus, superior biocompatibility and enhanced corrosion resistance when compared to more conventional stainless steel and cobalt-based alloys. Ti-13Nb-13Zr is a titanium alloy specifically developed for surgical implants. In this work, highly porous titanium foams, with porosities above from 50%, are reached using an efficient powder metallurgical process, which includes the introduction of a selected spacer into the starting powders. Samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering. The samples presented a Widmanstättenlike microstructure in an open cellular morphology with pore size between 200-500 μm.

Microstructural Investigation of Routes for Gamma Titanium Aluminides Production by Powder Metallurgy

The alloy design and efficient routes of TiAl processing are important technological challenges for the development of new aerospace systems. Gamma-TiAl alloys are potential replacements for nickel and conventional titanium alloys in hot sections of turbine engines, as well as in sub-structures of orbital platform vehicles. Powder metallurgy (P/M) of Ti-based alloys may lead to the obtainment of components having weak-to-absent textures, uniform grain structure and higher homogeneity compared with conventional wrought products. This paper aims to investigate the microstructural evolution and densification aspects involved in the obtainment of Ti-48Al-2Cr-2Nb (at.%) alloy by three P/M-processing routes. Samples were prepared from elemental and pre-alloyed powders mixed for 2 h, followed by cold uniaxial and isostatic pressing followed by sintering and hot pressing stages between 1100°C up to 1400°C, for 1 h. After metallographic preparation, sintered samples were characterized by means of scanning electron microscopy (SEM) in the backscattered mode (BSE), X-ray diffraction (XRD), and density measurements. The results showed the potential of TiAl pre-alloyed powders to prevent Kirkendall porosity. A full lamellar microstructure was obtained by the pressureless route while a duplex microstructure was observed in samples produced by the hot pressing route.

Evaluation of Press-and-Sinter Processing Parameters in Titanium Hydride Powder Metallurgy

The use of hydrogenated titanium powders combined with traditional PM techniques may lead to a significant reduction in the manufacturing costs of titanium components. In this work, the advantages and limitations of the use of TiH2 powder consolidated through the conventional press-and-sinter method were investigated. Processing parameters related to the compaction and sintering were studied for a TiH2 powder in the particle sizes <355 μm, <150 μm and <45 μm. Optimized compaction conditions were achieved by using admixed lubricant and compaction pressure of 800 MPa. The mechanisms involved in the compaction of powders were detailed through the fit of compressibility data to a theoretical model originally developed for titanium powders. Densification of samples was favored by the reduction in particle size and increase in sintering temperature up to 1300 °C. The positive effects of hydrogen release during dehydrogenation were verified through the results of sintered densities and the reduction of oxygen levels. Limitations were observed mainly regarding the flowability of powders and the difficulty to achieve full densification.

Improvement of Tribological Properties by Titanium Nitride Deposition in Titanium Alloys Produced by Powder Metallurgy

Titanium nitride (TiN) is a hard material, often used as coating to improve the wear properties of titanium alloys in machining, implant and aerospace applications. Electron Beam Physical Vapor Deposition (EB-PVD) is a technique which a target anode is bombarded with an electron beam given off by a charged tungsten filament under high vacuum, producing a thin film in a substrate. In this work, results of TiN films depositions on Ti-13Nb-13Zr substrates by EB-PVD are studied. Titanium targets were obtained by a purified ingot and the substrates produced by powder metallurgy. Sintered samples of Ti-13Nb-13Zr and TiN layers were characterized by X-ray diffraction, scanning electron microscopy, Vickers microhardness and wear tests. The TiN films presented high hardness values, continuity and large thickness. The coatings improved the tribological properties of the substrate due to high adhesion and low wear rate.

TiN/ZrN Multilayer PVD Coatings on Titanium Alloys Produced by Powder Metallurgy

Multilayer coatings are synthetic structures constituted by alternate layers of different materials. The technological applications of the multilayer coatings can involve optical, electromagnetism and wear areas. The target of this work is the production of multilayer TiN/ZrN coatings by Electron Beam Physical Vapor Deposition (EB-PVD) over titanium alloys produced by powder metallurgy. P/M-Ti-35Nb-7Zr-5Ta cylindrical samples used as substrates were produced by mixing of the elemental powders with subsequent cold pressing steps and sintering at 1400°C, in high vacuum. TiN/ZrN coatings were obtained by evaporation of alternating Ti and Zr cylindrical targets. The multilayers were characterized by optical and scanning electron microscopy (SEM), chemical analysis via energy dispersive spectrometry (EDS) and Vickers indentation. Besides the possibility of obtaining several layers, the results show coatings with coherent columnar structure, low discontinuity, large and homogenous thickness and high adhesion to substrate.

Titanium Nitride Deposition in Titanium Implant Alloys Produced by Powder Metallurgy

Titanium nitride (TiN) is an extremely hard material, often used as a coating on titanium alloy, steel, carbide, and aluminum components to improve wear resistance. Electron Beam Physical Vapor Deposition (EB-PVD) is a form of deposition in which a target anode is bombarded with an electron beam given off by a charged tungsten filament under high vacuum, producing a thin film in a substrate. In this work are presented results of TiN deposition in targets and substrates of Ti (C.P.) and Ti-13Nb-13Zr obtained by powder metallurgy. Samples were produced by mixing of hydrided metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering between 900°C up to 1400 °C, in vacuum. The deposition was carried out under nitrogen atmosphere. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. It was shown that the samples were sintered to high densities and presented homogeneous microstructure, with ideal characteristics for an adequate deposition and adherence. The film layer presented a continuous structure with 15m.

Interstitial Control in Titanium Alloys Produced by Powder Metallurgy

The titanium alloys are used for applications that demand high performance, including surgical implants and aerospace applications. Powder metallurgy is an advantageous alternative for titanium parts production with complex geometries at a relative low cost. Despite that, it is verified that the introduction of interstitial elements (oxygen, nitrogen and carbon) wile processing these alloys, though can increase hardness and mechanical resistance, which is frequently related to the reduction of ductility and fragility increase. The objective of this work is to investigate the influence of the interstitial elements in commercially pure Ti and Ti-13Nb-13Zr alloy produced by powder metallurgy (P/M). Samples were produced by the mixing of hydrided metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering at 1400 °C, in vacuum. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. The interstitial content was analyzed by Leco equipment. It was shown that the samples were sintered to high densities with a Widmanstatten microstructure. The oxygen and nitrogen contents are above the ELI (Extra Low Interstitial) and the critical issues were identified in the original blended elemental route.

Ti-13Nb-13Zr Production for Implant Applications

Powder metallurgy (P/M) of titanium alloys may lead to the obtainment of components having weak-to-absent textures, uniform grain structure and higher homogeneity compared with conventional wrought products. The production of the Ti-13Nb-13Zr alloy by P/M starting from blended elemental (BE) powders is a cost-effective route considering its versatility and also for allowing the manufacture of complex parts. This alloy due its high biocompatibility and lower modulus of elasticity is a promising candidate for implants fabrication. Samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering in order to identify the microstructural evolution. Sintered samples were characterized for phase composition, microstructure, microhardness and density. The surface topography of the samples was studied by means of atomic force microscopy (AFM). It was shown that the route is adequate to reach high densities with homogeneous microstructure. Representative AFM images allowed distinguishing a lamellar structure caused by the different phases that are present in the surface of the specimens.