Marcello Filgueira

A Novel Method for Obtaining Polycrystalline Diamond Cutters

The present work comprises a study about the possibility of obtaining polycrystalline diamond cutters through a novel method of sintering both layers at the same time. This possibility was tested through the sintering of a diamond layer over a hard metal (WC+15wt%Co) support under conditions of 5.0 and 6.5 GPa of pressure and 1400 to 1600º C of temperature. The sintering conditions were imposed in two ways: directly, or with pre-sintering. The samples were tested by measuring microhardness, wear resistance, densification, and SEM. The results of the tests have shown the possibility of obtaining good quality inserts by sintering both layers of compacted powder.

Use of PM Fe-Cu-SiC composites as bonding matrix for diamond tools

Abstract The use of the system Fe–(5,10,15,20)%Cu with the addition of 1% weight of silicon carbide (SiC) as bonding matrix for diamond tools was investigated in the present work. The diamond metallic composites were manufactured via conventional powder metallurgy and sintered at 1050 and 1150°C. Evaluation of the composites included the measurement of the level of shrinkage/swelling, Brinell hardness and wear resistance. Microstructure was investigated via scanning electron microscopy (SEM). The results show that temperature of 1150°C presented the best sintering condition for the composites. Among the studied compositions, the alloy with 20%Cu content presented the best wear performance as metallic bonding matrix for diamond composites.

Some peculiarities of the diamond micro-powder sintering

Diamond micro-powders of 28/20 μm mean particle size were sintered under conditions of high pressure of 6.0 and 8.0 GPa at temperatures of 1600, 1700, and 1800 °C during various sintering times, aiming to obtain polycrystalline compacts with required strength. The experiments were carried out by using an anvil type high pressure device with toroidal concavity of 13.5 mm diameter. It was obtained samples with 4.5 mm diameter and 5.0 mm height. It was plotted the polycrystalline diamonds density dependency as a function of the process duration under the above mentioned sintering conditions. The kinetics of powder consolidation was studied by X-ray diffraction, which allowed the establishment of the correlation between the (3 3 1) plane enlargement of diamond and the structural transformations that took place during sintering. Another objective was the study of the graphitization kinetics of diamonds under the action of the sintering parameters. It was concluded that over the established consolidation mechanisms, also acts the partial shear mechanism.

Sinterização da liga WC/10Co por altas pressões

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 KIc =11MPa.m½.

Processing of diamond composites for cutting tools by powder metallurgy and rotary forging

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 O=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.

On the Compacting of Powders of the Systems Fe-Cu and Fe-Cu-Diamond

This work aims at the study of the behavior of the powder systems Fe-Cu e Fe- Cu-Diamond under compaction, using the stoichiometries Fe-20Cu (wt%) e Fe-20Cu-4 Diamond (wt%). It was applied pressures at the interval 100 to 600 MPa, and it was used the Balshin and Rong-De’s equations to establish the exact behavior of the systems under pressing: accommodation, plastic deformation and particle’s rearrangement.

Caracterização de tubo e adesivo utilizados em tubulações de plástico reforçado com fibras de vidro aplicados em plataformas marítimas

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.

Study of the TiC Coating on Powder Metallurgy Diamonds Tool's Performance

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.

Processing and Mechanical Properties of PM Processed Fe-Cu-Co Alloys

In this work, a study to process and characterize Fe-Cu alloys with reduced Co content is shown. The Fe-Cu-Co alloys were processed by elemental blending of powders of the system Fe- 15%wtCu with various amounts of Co, pressing at 350MPa, and sintering at 1150°C/25min./10-2 mbar. The sintered microstructure was observed. It was conducted hardness and wear tests, aiming to define the ideal Cu addition for future use in impregnated diamond tools. It was observed that higher Co contents results in improved hardness and wear resistance in the studied Fe-Cu alloys.

Thermal properties of WC-10 wt. (%) Co alloys

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.