O titânio é um metal nobre e possui excelentes propriedades biomecânicas, podendo assim ser plenamente aceito pelo organismo humano. A grande demanda na utilização de implantes dentários, fabricados a partir de ligas de titânio traz consigo um aumento significativo na geração de resíduos (cavacos), resultantes dos processos de usinagem empregados. Com o objetivo de reduzir os impactos ambientais, soluções alternativas para a reutilização de tais resíduos têm sido estudadas. O carboneto de titânio (TiC) possui elevada dureza, o que potencialmente permitiria a sua utilização como reforço em revestimentos antidesgaste aplicados em equipamentos das indústrias sucroalcooleira e mineradoras. Neste trabalho cavacos de ligas a base de titânio foram processados e utilizados como matéria prima para a fabricação de consumíveis experimentais de soldagem. Cordões de solda foram produzidos sobre amostras de aço-carbono por soldagem a arco elétrico com proteção gasosa e eletrodo de tungstênio (tradução do termo inglês GTAW). A caracterização microestrutural do metal de solda foi realizada por MEV e difração de raios-X. O comportamento mecânico dos revestimentos foi analisado por meio de um ultramicrodurômetro digital. Verificou-se que a microestrutura do metal de solda era composta por partículas não prismáticas de alta dureza distribuídas em uma matriz ferrítica. Medidas feitas por microanálise EDS mostraram diferenças na concentração de titânio entre a matriz e as partículas duras, onde maiores teores deste elemento foram identificados. A análise cristalográfica confirmou que houve a formação de carbonetos de titânio envoltos por uma matriz de ferrita.

Titanium element is a noble metal and owns excellent biomechanical properties. The necessity for utilization dental implants fabricated with titanium alloys have caused an increased in generation of residue as a result of fabricating processes. Aiming to reduce the environmental impact, alternative solutions for reutilization of these residues have been studied. Titanium carbide (TiC) has high hardness and can be applied as coating reinforcement against wear. In this work, chips of titanium cast were processed and used in the fabrication of experimental hardfacing consumables. Coatings were produced in cast steel specimens using the GTAW process. The microstructures were investigated by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanical behavior of the coatings was analyzed by a dynamic ultra-micro hardness tester. The microstructure of the welding metal was composed of particles non-prismatic and high hardness surrounded by a ferritic matrix. The measures made by electron dispersive spectroscopy (EDS) showed difference of the concentration of titanium trough the particle, where larger contents of titanium were found, and the matrix. The crystallographic analyses reinforced the formation of titanium carbides embedded in a ferrite matrix into welding metal.

Equipamentos usados nas usinas sucroalcooleiras e de extração mineral são submetidos a condições severas de desgaste abrasivo. Revestimentos duros são usualmente aplicados para reparar este tipo de dano, sendo bastante empregados consumíveis de soldagem contendo altos teores de cromo e carbono. No presente trabalho visa investigar a microestrutura de revestimentos duros formados com a fusão de cavacos de titânio puro ASTM F67 grau 4, material usado na fabricação de implantes odontológicos. Misturas com diferentes formadores de carbonetos (Fe-Cr e Fe-Nb como aditivos) também foram testadas. Revestimentos feitos com duas camadas de cavacos "puros" (Ti), cavacos com Fe-Cr (Ti-Cr) e cavacos com Fe-Nb (Ti-Nb) foram depositadas sobre peças de aço-carbono por soldagem TIG/GTAW. A microestrutura das camadas foi observada com microscópio óptico e por microscópio eletrônico de varredura equipado com microanálise. A caracterização microestrutural revelou que a distribuição de carbonetos varia significativamente com a natureza química dos aditivos usados. A microanálise mostrou que houve a formação de carbonetos com composição química complexa no seio do metal de solda, cuja estequiometria foi determinada com análise por difração de raios-X. Carbonetos mistos do tipo MC e cementita foram identificados. Os resultados apresentados indicam que a aplicação de cavacos de titânio ASTM F67, como insumo para formação de carbonetos, pode contribuir para melhorar a resistência ao desgaste em comparação aos tradicionais revestimentos duros com carbonetos de cromo.

Equipments of the sugar-cane plants and mineral extraction are submitted to severe abrasive wear conditions. Welded hardfacing are usually applied to repair that kind of damage where commercial chromium/carbon-rich welding consumables have usually been employed. In the present work was investigated the microstructure of experimental hardfacings made by addition of residues (chips) collected from machining of ASTM F67 (unalloyed Ti, grade 4) alloy. Mixtures with different carbide-formers (Cr/Nb ferro-alloys) were also tested. Two layers of "pure" chips (Ti), chips plus Fe-Cr (Ti-Cr), and chips plus Fe-Nb (Ti-Nb) were applied on low-carbon steel specimens by GTAW/TIG process. The microstructure of hardfacing layers was observed by optical and scanning electron microscopy (SEM) equipped with EDS microanalysis. The microstructural characterization has determined that carbide distributions change significantly with the chemical nature of the hardfacing. SEM observations coupled with EDS microanalysis have confirmed the formation of complex carbides within metal weld, whose stoichiometry was determined by X-rays diffraction (XRD) analysis. Mixed carbides MC-type and some cementite have been found. As a result it was suggested that using of ASTM F67 chips as carbide formers for composition of welding consumables can contribute to improve wear resistance of hardfacings, if compared with traditional chromium-based hardfacings.

Grain size refinement is one of the most efficient strengthening mechanisms applied to modern High-Strength Low-Alloy steels (HSLA) because yield strength and toughness are both improved. This paper discusses the distribution of carbides by using transmission electron microscopy (TEM) in a low-carbon steel with ultrafine grained (UFG) ferrite. Fine cementite particles were formed during water quenching due to the auto-tempering of highly distorted martensite. Other fine particles observed under the same condition were nucleated due to the presence of carbide formers such as niobium, titanium and vanadium. TEM analysis showed that cementite particles underwent Ostwald ripening during warm rolling but they were still able to inhibit ferrite grain growth, which was maintained 1µm size approximately.

The ASTM F1295/Ti-6Al-7Nb alloy present mechanical properties and biocompatibility very attractive for application in medical and dental implants. In this context, processing of these Ti-based alloys by severe plastic deformation (SPD) has been extensively reported recently. However, the mechanical properties of equal channel angular pressed (ECAP) ASTM F1295 alloy are still a matter of research. In the present study, Ti-6Al-7Nb samples were processed by ECAP following thermomechanical processing which effects on the microstructure of Ti-6Al-7Nb alloy were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The analyses have shown that the microstructure was composed by ultrafine grains (UFG) with sizes ranging from 200 to 400 nm. Ring-type selected area electron diffraction patterns (SAEDP) suggested the co-existence of low- and high-angle grain boundaries. Some regions of the samples have presented evidences of the presence of grains with unfavorable orientation to the plastic deformation. These grains can act as rigid bodies and concentrate the deformation in its surrounding areas, as an "open-die grain" mechanism. Such deformation mechanism could be attributed to the differences in the plastic behavior between the alpha and beta titanium phases.

Ti-6Al-7Nb alloys are being evaluated for biomedical applications, in substitution of the more conventional Ti-6Al-7V. Both types of alloys present a microstructure containing the α and the β phases, which result in good compromise for mechanical applications. In the present work Ti-6Al-7Nb alloys were processed by High Pressure Torsion (HPT), varying the number of revolutions and thus the total imposed strain. X-Ray Diffraction (XRD) results revealed the formation of different crystallographic textures in samples subjected to HPT. Microhardness distribution, across the diameters of the disks, is rather homogeneous for all samples, with higher values for those subjected to 03 and 05 turns. Transmission electron microscopy (TEM) micrographs have showed that an ultra-fine grained microstructure was obtained in all the samples.

This paper quantifies the effects of milling conditions on surface integrity of ultrafine-grained steels. Cutting speed, feed rate and depth of cut were related to microhardness and microstructure of the workpiece beneath machined surface. Low-carbon alloyed steel with 10.8 µm (as-received) and 1.7 µm (ultrafine) grain sizes were end milled using the down-milling and dry condition in a CNC machining center. The results show ultrafine-grained workpiece preserves its surface integrity against cutting parameters more than the as-received material. Cutting speed increases the microhardness while depth of cut deepens the hardened layer of the as-received material. Also, deformations of microstructure following feed rate direction were observed in workpiece subsurface.