Abstract Ti-6Al-4V and TiAl-based alloys are widely used for fabricating the implantable orthopedic devices and automotive components, respectively. Ti6Si2B-based alloys are attractive for use in orthopedic components because their higher hardness, superior biocompatibility and corrosion resistance in simulated body fluid than Ti and Ti-6Al-4V alloy. Limited information on Ti6Si2B stability in Co-dopped 67Ti-22Si-11B alloys are available in literature. This work presents the effect of cobalt doping and milling time on microstructure and Vickers microhardness of 65Ti-2Co-22Si-11B and 61Ti-6Co-22Si-11B (at-%) alloys produced by spark plasma sintering at 1100 oC for 12min using 20MPa. Samples were characterized by X ray diffraction, scanning electron microscopy, energy dispersive spectrometry, laser particle size analysis, and Vickers microhardness. Sintered alloys with 2 and 6at-%Co indicated the major presence of Ti6Si2B and Ti5Si3 dissolving up to 2.7 and 4.2 at-%Co, respectively, besides the minor precipitates of CoTi2 (4.4-16.7at-%Si) and CoTi (4.6-4.7at-%Si). Vickers microhardness of the sintered 65Ti-2Co-22Si-11B and 61Ti-6Co-22Si-11B alloys were in the range of 950-1050 and 1050-1150HV, respectively. Although the increase from 2 to 6at-%Co has reduced the Ti6Si2B stability, the Co-rich phases increased their hardness values up to 1150HV (11.3GPa), which are superior than those of commercial Ti alloys used for joint orthopedic components and automotive rotating parts.

ABSTRACT With the aim of introducing permanent prostheses with main properties equivalent to cortical human bone, Ti-diamond composites were processed through powder metallurgy. Grade 1 titanium and mixtures of Ti powder with 2%, 5% and 10 wt% diamond were compacted at 100MPa, and then sintered at 1250°C/2hr/10-6mbar. Sintered samples were studied in the point of view of their microstructures, structures, yield strength and elastic modulus. The results showed that the best addition of diamonds was 2 wt%, which led to a uniform porosity, yield strength of 370MPa and elastic modulus of 13.9 GPa. Samples of Ti and Ti-2% diamond were subjected to in vitro cytotoxicity test, using cultures of VERO cells, and it resulted in a biocompatible and nontoxic composite material.

WC/Co is widely used as cutting tools, because has a unique combination of high strength, hardness, toughness, and moderate stiffness, especially with fine grained WC and finely distributed cobalt. WC/Co powder mixture sinters by different methods such as vacuum sintering, microwave sintering and SPS. High pressure high temperature (HPHT) sintering is a proposed method that can result in better distribution of cobalt and avoid undesirable phases by using high pressure, high temperature and very short sintering time. In this study, a powder mixture of WC- 10 wt% Co was sintered by HPHT at 1500 to 1900ºC under a pressure of 7.7 GPa for 2 minutes. Microstructural/structural analyses were performed by SEM/EDS. Hardness and compression test were also done to obtain the effect of sintering parameters. It was found that HPHT sintering method can be used to produce WC/Co hardmetal with low sintering time and high production rate. It was realized that increasing sintering temperature in HTHP sintering method results in increasing density but hardness and compression strength increase by increasing sintering temperature up to 1800 ºC and then decrease.

Many of the applications of diamonds expose them to high temperatures and atmospheres containing oxygen. Under these circumstances two important phenomena responsible for the thermal damage of diamonds are: oxidation and graphitization. It is well known that coatings on diamonds provide a better performance, but the amount of information in literature about the protective mechanism of these coatings is very scarce. The present work proposes a study about the thermal damage effect on diamonds with titanium (Ti) coating comparing with diamonds without it. Samples of uncoated diamonds and Ti- coated diamonds were heat treated at 1200 °C during different periods of time and characterized prior to and after the treatments. Differential thermal analysis (DTA) was performed to observe the temperatures that transformations in diamonds occur. The analysis of phases present in the samples and the observation of new phases formed were carried out by means of X-ray diffraction (XRD). In order to observe the diamond surface and how the chemical elements are distributed in it, the samples were analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results prove the protective capability of the Ti coatings, clarifying the protective mechanism against the thermal damage.

Some diamond tools use iron in their composition, and it is known that iron is a strong catalyst for the graphitization of diamonds. This graphitization occurs mainly during the processing of composite materials - conventional sintering or hot pressing, and during cutting operations. This work studies the effect of TiC coating on diamond, on structure, microstructure and mechanical properties of the processed composites. Samples were prepared by mixing powders of Fe (40 μm) and diamond (425 μm), and subsequent hot pressing at 35MPa/900 °C, during 3 minutes. Microstructural aspects were observed by SEM, and iron diffusion on diamond was studied by EDS. Structural analyses were performed by X-ray diffraction and Raman spectroscopy. Compressive tests were carried out, as well as the wear resistance of the diamond composites. The importance of employing coated diamonds was stablished. It was observed that iron did not activated the graphitization of diamond crystals.

Na indústria de exploração e produção de petróleo, principalmente no setor offshore, os plásticos reforçados por fibras de vidro (PRFV) têm apresentado grande destaque. Isso se deve à intrínseca capacidade destes de resistir à corrosão em ambientes salinos, bem como serem materiais que apresentam elevada resistência mecânica específica. O presente trabalho buscou caracterizar tubo e adesivo utilizados em plataformas marítimas. Para tanto, as técnicas utilizadas foram: espectroscopia na região do infravermelho com transformada de Fourier (FTIR), análise termogravimétrica (TGA), análise termodinâmico-mecânica (DMTA) e temperatura de amolecimento de Vicat. Amostras do tubo de PRFV e dos componentes do adesivo (denominados de A e B) foram estudadas individualmente. Além disso, foram confeccionadas misturas, em massa, nas seguintes proporções: 40%A-60%B, 50%A-50%B e 60%A-40%B. Foi possível determinar a composição e a estrutura química dos materiais, além do comportamento mecânico à degradação térmica. Foi verificado que adesivo e tubo apresentaram desempenho satisfatório à temperatura ambiente quanto à degradação e à rigidez. Por outro lado, quando submetido ao calor, principalmente os adesivos, apresentaram queda brusca de desempenho.

Glassfiber reinforced plastics (GFRP) have been applied in the offshore industry owing to their high resistance to corrosion and high specific mechanical strength. The present work aimed at characterizing pipes and adhesives used in offshore platforms in order to evaluate the thermo-mechanical performance of these materials. The techniques used were: Fourier transform infrared spectroscopy (FTIR), thermogravimetry analysis (TGA), dynamic mechanical thermal analysis (DMTA) and Vicat softening temperature. Specimens of GFRP pipe and adhesive components (referred to as A and B) were evaluated individually. The adhesive samples were made in the following ratios (% weight): 40%A-60%B, 50%A-50%B and 60%A-40%B. The results showed it to be possible to determinate the composition and structure of the materials, as well as the mechanical behavior regarding thermal degradation. The adhesive and pipe exhibited satisfactory performance at room temperature, with regard to degradation and stiffness. Nevertheless, at higher temperatures, both materials, especially the adhesives, presented abrupt strength reduction.

In this article, photothermal techniques were used in order to determine some thermal properties: diffusivity, conductivity, effusivity and specific heat capacity of WC-10 wt. (%) Co six samples subjected to different sintering processes. The samples were sintered using high pressure - high temperature (HPHT) sintering system. The open cell photoacoustic (OPC) used to measure thermal diffusivity is described in detail. The values of thermal properties here measured and evaluated are consistent to those previously reported in the literature.

Este trabalho mostra a rota de processamento de um compósito diamantado à base de bronze 4% em peso diamante, para aplicação direta como fios diamantados, e serras lineares de desmonte e corte de rochas ornamentais. Esta rota consiste do emprego das técnicas de compactação da mistura pulverulenta, sinterização e forjamento rotativo. Ensaios de tração revelaram uma resistência de 230MPa para o compósito diamantado de 1,84mm de diâmetro. Microscopia eletrônica de varredura mostrou a distribuição dos cristais de diamantes ao longo do compósito durante a sua manufatura, assim como a adesão dos diamantes para com a matriz de bronze. Testes de corte feitos com fios do compósito bronze 4% em peso diamante, revelaram um desempenho da ordem de 4 vezes superior ao dos discos diamantados de corte, contudo, seu desempenho é cerca de 5 a 8 vezes inferior ao dos fios diamantados perolados, devido à baixa resistência à abrasão da matriz de bronze, baixa adesão entre o par bronze-diamante, devido ao uso de diamantes não metalizados.

This paper shows the manufacture route of the bronze 4% weight diamond composite rope for direct application as diamond wires, and linear saws in the slabbing and cutting of dimension stones. This route consists of powder mix compaction, sintering and rotary forging techniques. Tensile tests were performed, reaching an ultimate tensile strength of 230MPa for the diameter of Æ=1.84mm. Scanning electron microscopy showed the diamond crystals distribution along the composite rope during its manufacture, as well as the diamond adhesion to the bronze matrix. Cutting tests were carried out with the external cutting rope, showing a probable performance 4 times higher than the diamond sawing discs, however its probable performance was about 5 to 8 times less than the conventional diamond wires (pearl system) due to the low abrasion resistance of the bronze matrix, low adhesion between the pair bronze-diamond due to the use of not metallized diamond single crystals.

Os compósitos a base de nitreto cúbico de boro (cBN) atualmente se destacam na usinagem de metais e ligas de dureza elevada, podendo substituir a retífica. A efetividade de utilização dos compósitos de cNB depende, em geral, do estudo da tenacidade do inserto. A obtenção de pastilhas de cBN, realiza-se sob altas pressões até 8 GPa e temperaturas de até 2000ºC. Em condições não hidrostáticas, as tensões internas têm valores significantes, diminuindo a vida útil da ferramenta. Para aumentar a tenacidade e a eficiência de uso foi proposto o tratamento térmico complementar em condições de vácuo sob temperaturas de até 1000ºC e tempo de 1hora. As pastilhas de cBN foram sinterizadas à pressão de 7,7 GPa e temperatura de 1600ºC. A composição da pastilha utilizada foi de 65%p de cBN e 35%p de ligante. Para determinação de nível de desgaste durante usinagem foi utilizado aço 4140 com dureza de 56-58HRc. Comparando a efetividade de usinagem das pastilhas de cBN obtidas com o compósito Elbor®, pôde ser notado que o tratamento térmico complementar aumentou a capacidade de usinagem da pastilha de cBN em 40%.

Cubic Boron Nitride (cBN) composites play an important role within metals and hardened alloys machining field, usually removing grinding from production processes. The effectiveness of cNB composites depends, in general, on insert toughness studies. Cubic boron nitride compacts are produced by sintering under high pressure high temperature (HPHT) conditions, up to 8 GPa and 2000°C. At non-hydrostatic parameters, internal stresses have significant values, decreasing tool life. In this study, the addicional thermal treatment (in vaccum, under temperatures up to 1000ºC for 1 hour) is proposed as a way for increasing toughness and tool efficiency. The parameters used for sintering were 7.7 GPa and 1600ºC, with samples composition of 65%w of cBN and 35%w of binder. Wear level was determined during machining of an AISI 4140 steel hardened to 56-58HRc. Comparing machining results of obtained samples and Elbor® composite, it could be noticed that the addicional thermal treatment improved cBN inserts machining capability in 40%.

Ligas de metal duro (WC/Co) são geralmente processadas pelas técnicas da metalurgia do pó, que compreende mistura dos pós elementares, compactação e sinterização por fase líquida, com ou sem a posterior prensagem isostática a quente (HIP). Uma nova rota de processamento de metal duro é aqui apresentada, chamada de altas pressões e altas temperaturas (HPHT). Neste trabalho foi estudada a sinterização da liga WC/10% pesoCo a 5GPa, nas temperaturas de 1200, 1300, e 1400ºC, para os tempos de 1 e 2 minutos. Os melhores resultados obtidos foram: densidade =95,6%, dureza HV45 =10GPa e tenacidade à fratura K Ic=11MPa.m½.

Hardmetal is usually processed by the conventional powder technology techniques: mix of WC + Co powders, compacting, and liquid phase sintering. A new method to process hardmetal parts are described here. Parts of WC/10%wt Co were processed by using high pressure and high temperature sintering. It was used the pressure of 5GPa, temperatures of 1200, 1300, and 1400ºC, and times of 1and 2 minutes of sintering. The best results was density =95,5%, hardness HV45 =10GPa and fracture toughness of K Ic =11MPa.m½.

O presente trabalho apresenta o processamento e ensaios abrasivos, referentes ao desenvolvimento de compósitos à base do sistema poliéster-SiC (carbeto de silício), e a avaliação da possibilidade de sua aplicação tecnológica nas coroas de polimento de rochas ornamentais, normalmente feitas à base do compósito cimento magnesiano (SOREL)-SiC. Com esta finalidade, compósitos foram produzidos utilizando-se concentrações variáveis de SiC (5-10-20-30-50-50%) proporcionais ao sistema poliéster-SiC, via mistura e posterior cura, mediante emprego de catalisador. Os compósitos foram submetidos a testes de desgaste, simulando uma situação de polimento de rochas ornamentais. Dentre os compósitos poliéster-SiC produzidos, as amostras que apresentaram melhores resultados foram as que possuem 50%p SiC. Estas superaram em 5 vezes as amostras de SOREL-SiC no desempenho de abrasão, porém as mesmas apresentaram um resultado 4,6 vezes maior em termos de perda de massa, levando a um "empate" no desempenho global.

This work deals with the processing and abrasive tests in polyester - SiC (silicon carbide) composites, and evaluation of their possible technological application in dimension stones polishing crowns - commonly made of magnesian mortar (named SOREL) - SiC. Composites were prepared with polyester concentrations of (5-10-20-30-40-50) weight % SiC, by mixing and curing. The composites were submitted to wear tests, simulating a dimension stone polishing operation. Optimized performance was achieved for samples with 50%wt SiC, which exhibited an abrasion resistance 5 times that of SOREL-SiC samples. However, the composite displayed a mass loss 4.6 times higher, thus pointing to an overall performance that is similar to that of SOREL-SiC samples.

We propose an original route to process diamond wires, denominated In Situ Technology, whose fabrication involves mechanical conformation processes, such as rotary forging, copper tubes restacking, and thermal treatments, such as sintering and recrystallisation of a bronze 4 wt.% diamond composite. Tensile tests were performed, reaching an ultimate tensile strength (UTS) of 230 MPa for the diameter of <FONT FACE=Symbol>Æ</FONT> = 1.84 mm. Scanning electron microscopy showed the diamond crystals distribution along the composite rope during its manufacture, as well as the diamond adhesion to the bronze matrix. Cutting tests were carried out with the processed wire, showing a probable performance 4 times higher than the diamond sawing discs, however its probable performance was about 5 to 8 times less than the conventional diamond wires (pearl system) due to the low abrasion resistance of the bronze matrix, and low adhesion between the pair bronze-diamond due to the use of not metallised diamond single crystals.

Cu-Nb microcomposites are attractive in magnet pulsed field technology applications due to their anomalous mechanism of mechanical strength and high electrical conductivity. In this sense, recently it was conceived the use of Cu 15% vol. Nb wires to operate as a high tensile strength cable for a diamond cutting tool (diamond wires) for marble and granite slabbing. The multifilamentary Cu 15% vol. Nb composite was obtained using a new processing route, starting with niobium bars bundled into copper tubes, without arc melting. Cold working techniques, such as swaging and wire drawing, combined with heat treatments such as sintering and annealing, and tube restacking were employed. The tensile property of the composite was measured as a function of the niobium filaments dimensions and morphology into the copper matrix, in the several processing steps. An ultimate tensile strength (UTS) of 960 MPa was obtained for an areal reduction (R = Ao/A, with Ao-initial cross section area, and A-final cross section area) of 4x10(8) X, in which the niobium filaments reached thickness less than 20 nm. The anomalous mechanical strength increase is attributed to the fact that the niobium filaments acts as a barrier to copper dislocations.