Papers by Author: Marcello Filgueira

Abstract: The substitution of cobalt, present in the commercial binder metal matrix commonly used by the industry, was analyzed: 25,2%Fe-49,5%Cu-24,1%Co – NEXT 100® by the niobium element of the Fe-Cu-Co system, obtaining 4 metal matrices: 28,34%Fe–56,66%Cu–15%Nb; 25%Fe–50%Cu–25%Nb; 21,67%Fe–43,33%C–35%Nb; 18,34%Fe–36,66%Cu–45%Nb. This study aims to evaluate the behavior of metal matrices to better choose the type of matrix to be used in the manufacture of diamond tools. The metal powders were blended according to the compositions of each metal matrix and then hot pressed at 800o /35MPa / 3min, thus occurring the sintering. The sintered samples of each metal matrix were conducted to the Abrasion Resistance test in order to verify the wear, for the accumulated times of 2, 6, 12 and 20 minutes. In these metal matrices, density, porosity and Vickers hardness (HV5) tests were performed to better understand the wear suffered by the samples. Thus, the metal matrix 25% Fe-50%Cu-25%Nb presented, in the general context of the properties and from the abrasive point of view, satisfactory results capable of replacing the NEXT 100 matrix.

Abstract: This work presents the structural characterization of Ti-10Si-5B and Ti-20Si-10B (at-%) alloys produced by high-pressure assisted sintering. Sintering was performed in air at 1100 and 1200 °C for 60 s using pressure levels of 5 GPa. Structural evaluation of sintered samples was conducted by means of scanning electron microscopy and energy dispersive spectrometry. Samples were successfully consolidated after sintering, which presented theoretical density values higher than 99%. The microstructures of the sintered Ti-10Si-5B and Ti-20Si-10B alloys revealed the presence of the Ti_SS, TiB, TiB₂, Ti₅Si₃, Ti₅Si₄, TiSi, and TiSi₂.phases. A small amount of Ti₆Si₂B was formed after high-pressure assisted sintering of the Ti-20Si-10B alloy (5GPa, 1100°C for 60 s) indicating that equilibrium structures were not achieved during short sintering times. No oxygen and carbon contamination was detected in structures of Ti-Si-B alloys after high-pressure sintering at 1100 and 1200 °C without controlled atmosphere.

Abstract: 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 influence of the behavior of the wear and adhesion, of iron-diamond composites, by considering the use of TiC coated diamonds. Samples were prepared by mixing powders of Fe (40 μm) and diamond (425 μm), and subsequent hot pressing at 35MPa/900°C, for a time of 3 minutes. It was evaluated the mechanism of wear, and the behavior of the samples during diametral compression test. It was used the cumulative times of 2, 6, 12 and 20 minutes during the testing of abrasion.

Abstract: Typically, diamond tools produced by Powder Metallurgy are very effective in cutting processes in general, because are used diamond composites for cutting action. In these tools, diamond abrasive grains are embedded in the metal matrix. Some of the most common examples of these tools are the cutting discs, abrasive crowns, drills and diamond wires. This work studies the Fe-Cu-Co-diamonds composites processed by the powder metallurgy techniques powders mixing and hot pressing at 850°C/35MPa/3 min. Microstructural analysis of composites as well as metal matrix-diamond adhesion was made by scanning electron microscopy-SEM after abrasion resistance tests. Compression tests were carried out to evaluate the elastic properties of composites, i.e., modulus of elasticity (E) and yield stress (σ_e), aiming at the assessment of the metal matrix-diamond adhesion. It was found satisfactory adhesion for the composites M2 and M3, with values σ_e = 360 MPa and 375 MPa, respectively. Keywords: diamond tools, powder metallurgy, composite Fe-Cu-Co-diamond.

Abstract: 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.

Abstract: In the rock-drilling industry, double layer polycrystalline diamond-hardmetal (Dia-HM) inserts for cutting tools are subjected to elevated levels of wear due to the high power involved in the process. A research performed by focusing on the wear mechanism has shown that the complexity of the actual industrial operation can be reproduced in laboratories. The present work developed a methodology to calculate the theoretical values of wear of drilling tools. The main parameter selected for this methodology was the amount of disaggregated rock. The information acquired through this methodology gives one a complete perspective about the application of Dia-HM inserts to be used in drilling tools.

Abstract: This work have like object to research the metallic matrix, Ni-Sn and Co-Sn, and subsequent to add up to diamond for analyses the possibility the to replace the Co with Ni in the metallic matrix for to act like binder for subsequent use in cutting tools. The metallic powders and the composites were mixed and then hot pressed and processed at 35MPa/800°C/3 min. In these sintered samples, it was made hardness HRB, wear resistance test and scanning electron microscopy for to identify which one matrix owns better mechanical resistance and diamond adherence required for diamond cutting tools.

Abstract: Inserts of drill bits used in perforation of wells are employed to cut many different kinds of stone. The material that shows the best performance on this application is the WC+Co+Diamond composite, obtained via powder metallurgy. However, heterogeneous microstructural aspects in these composites may impair their efficiency. On this work, WC+6%Co-based composites were obtained via high pressure sintering at 5.0 GPa, with diamonds, WC and Co powders. The particle size of the diamond was 400/315 μm, and for the WC and Co, 100/63 μm. Part of the samples also received 2wt%CrB2 as a doping agent. Wear tests were carried out in an abrasimeter with a maximum axial load of 50 kg. Linear and volumetric wear indices achieved values of 821∙10-6 g/m and 10.7 g/m3, that are superior to inserts produced via conventional powder metallurgy.

Abstract: Powder metallurgy-based technologies of saw blades production for stone cutting normally uses cobalt as binder agent. Cobalt was chosen for that purpose because it provides improved properties, high wettability and good adhesion between dispersed diamond particles. In addition to its excellent physical properties, cobalt also shows a positive behavior associated with the control of diamond graphitization at temperatures up to 1000°C. In this work, an experimental planning method supported by a mathematical algorithm was used to study the influence of doping agents incorporated into cobalt-based binders. The consequences on the wear resistance of saw blades, as well as on other physical and mechanical properties of the “diamond-cobalt-doping agent” composites were investigated. Cr3C2, Si, Ni and Fe were used as doping agents. Experimental tests were carried out using granite as a base material for wear and cutting operations.

Abstract: Nanometric powders of WC with 10 weight% Co were mixed in high-energy mill. Compaction was performed at 200MPa and processed by the technique of high pressure and high temperature (HPHT). Sintering conditions were P = 5GPa, T = 1300-1400-1500° C, t = 2-4 min. For comparative purposes, samples were conventionally sintered at T = 1400° C, t = 45 min, vacuum of 10-2 mbar.