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Low boron steels are the only class of steel capable of forming a fully martensitic microstructure after hot stamping when a cooled tool is used, and the maximum stress can reach 1500 MPa. The purpose of this work is to study the applicability of 22MnB5 sheet metal as protective masks in hot forging dies. Sheets that were 1.3 mm thick were cut in samples of 110 mm diameter and heat treated in conditions similar to direct hot stamping and placed on the hot forging die. Cycles of 25, 50, 75, and 100 forgings were performed, and at each cycle, the metallic mask was replaced for characterization. Microhardness profiles, micrographic analysis by optical and electron microscopy, and profilometry profiles were used to determine the occurrence of surface wear on the masks after each forging cycle. The main types of superficial wear were abrasive and plastic deformation. However, the masks showed high resistance to wear and did not present failures that would make them unusable until the studied condition of a cycle of 100 forgings.

Large parts such as shafts for wind turbines are hot forged by upset and drawing. The repetitive heating, deformation, and cooling cause different metallurgical phenomena which directly influence the material behavior during and after the forming process. Particularly, while forging these large size parts, the temperature distribution does not remain uniform. This warrants a systematic study on heating and forging workpieces at variable temperature and austenitizing times. In this work, the influence of austenitizing time and temperatures on the microstructural evolution of the 42CrMo4 steel has been investigated. Samples have been austenitized and maintained at temperatures of 900°, 1000°, 1100°, and 1200 °C for 22, 66, and 200 min each and subsequently forged and quenched. The results have shown 42CrMo4 presented a complete recrystallized microstructure only when austenitized at 1200 °C for 200 min. Microhardness profiles have shown that increasing austenitizing time combined with higher temperature decreases the microhardness values in agreement with the decrease in resulting force; thereby, the related metallurgical phenomena of recovery and recrystallization cause material softening.

Biodegradable metallic materials (BMMs) are expected to corrode gradually in vivo after providing the structural support to the tissue during its regeneration and healing processes. These characteristics make them promising candidates for use in stents. These endoprostheses are produced from metal alloys by casting and thermomechanical treatment. Since porous alloys and metals have less corrosion resistance than dense ones, the use of powder metallurgy becomes an option to produce them. Among the metals, iron has been proposed as a material in the manufacturing of stents because of its mechanical properties. However, even then it is unclear what toxicity threshold is safe to the body. Thus, the objective of this research was to verify the biocompatibility of sintered 99.95% and 99.5% pure iron by powder metallurgy in vitro with Adipose-derived mesenchymal stromal cells (ADSCs) and in vivo with a Wistar rat model. Herein, characterizations of iron powder samples produced by the powder metallurgy and the process parameters as compression pressure, atmosphere, sintering time and temperature were determined to evaluate the potential of production of biodegradable implants. The samples obtained from pure iron were submitted to tests of green and sintered density, porosity, microhardness, hardness and metallography. The biocompatibility study was performed by indirect and direct cell culture with iron. The effects of corrosion products of iron on morphology, viability, and proliferation of ADSCs were evaluated in vitro. Hemolysis assay was performed to verify the hemocompatibility of the samples. In vivo biocompatibility was evaluated after pure iron discs were implanted subcutaneously into the dorsal area of Wistar rats that were followed up to 6 months. The results presented in this paper validated the potential to produce biodegradable medical implants by powder metallurgy. Both iron samples were hemocompatible and biocompatible in vitro and in vivo, although the 99.95% iron had better performance in vitro than 99.5%.

Incremental Sheet Forming (ISF) and particularly its Single Point (SPIF) variant has been studied intensively over the last years given the potential for low-cost prototyping and small batches production. Numerical and experimental works have been covering a widespan of materials and geometries. This paper fills an important gap regarding studies of the SPIF process applied to brass alloys, and particularly the commonly used Cu-35Zn brass alloy. Despite being a material widely used in industry for centuries, with excellent cold formability and innumerous applications, there is still no relevant information on the mechanical response and properties of this material under SPIF. This research is based in SPIF experiments with brass alloy sheets with different thicknesses (0.50, 0.70 and 1.00 mm), to obtain data such as forming forces or forming fracture lines to be compared against standard forming limit diagrams or against other materials under ISF. Other data like friction during the process was evaluated as well. Fifteen sets of experiments were conducted, using different values of step down (0.10, 0.50 and 1.00 mm) and two forming tools with diameters 10 and 15 mm.

The aim of this work is to analyse options of different powder metallurgy tools design with upper punch adapted with springs and its benefits with regards green density of the parts compacted in hydraulic press. Crack of the parts also were observed.

This paper is intended for the analysis of the fabrication of Thermoelectric Materials with emphasis on the use of Powder Technology including the use of Powder Technology. Main characteristics of them are considered. The recycling of thermoelectric material pieces is shown.

Metal injection molding (MIM) is a near-net-shape manufacturing process suitable for the production of small-size and complex-shape components. As a cost-effective and flexible manufacturing method, it may have distinct advantages over other methods when it comes to the manufacturing of implantable medical devices. However, up till now, the potential for MIM to be employed in the commercial-scale manufacturing of implantable medical devices has been insufficiently exploited. In the present research, an attempt was made to produce porous pure iron, as a metallic degradable biomaterial potentially for stent application, via the MIM route. The effects of iron powder loading and sintering temperature on the porosity, microstructure, mechanical properties, surface properties and in vitro degradation behavior of MIM iron were investigated. The results obtained were compared to those of cast iron. It was found that the amount of porosity retained in the as-sintered specimens had a major effect on their surface and mechanical properties. MIM iron exhibited strengths between those of magnesium alloys and 316 L stainless steel and very high ductility — a specially required property of stent materials. Its degradation rates in Hank's solution were superior to the degradation rate of cast iron. Interestingly, the material made from the feedstock containing 66% of iron powder, above the critical powder loading, showed the highest elongation and a good in vitro degradation rate. In conclusion, MIM is a promising method to be developed as a new route to produce thin-wall tubes for biodegradable stents.

In this study the soft magnetic alloy Fe-3Si-0.75P (wt%) was obtained by mechanical alloying through powder metallurgy. The processing included the formulation of metallic powder, wet milling for 1 h, 3 h, 6h and 9 h, in an attritor mill using alcohol P.A. as a lubricant. Cold compaction was then performed in a floating die under 600 MPa pressure and, finally the ring-shaped test specimens were sintered at 1150 °C for 1h. The electrical, physical and magnetic properties were then analyzed using the following assays: Laser granulometry, density, metallography, hysteresis curve and AC permeability, resistivity and XRD. The results showed a strong influence of milling time on magnetic properties of the alloy. There was a decrease in grain size with the milling time, which is likely the cause of increased in magnetic properties.

This work describes the development and manufacture of micro and meso extrusion dies used to extrude metal materials. The die design was based on different extrusion angles and diameters of input materials. An extrusion die was made to input material measuring 1 mm and for reduction to 0.8 mm with a 30° angle of extrusion. For the same diameter of material, another two dies were manufactured with extrusion angles of 45° and 60°. For meso sized extrusion, another three dies were made and the diameter of the input material was 4 mm with a reduction to 3 mm and extrusion angles of 30°, 45° and 60°. During the machining of the extrusion dies, high speed steel (HSS) drills were used with a tip angle according to the extrusion angles. After machining, the dies were treated thermally and polished to diminish the friction coefficient between the part to be extruded and the die. The results of the machining process indicate that extrusion dies can be manufactured using quick HSS drill and polishing can be done using diamond paste with satisfactory results.

This work has the objective of evaluating the effect of electromagnetic stirring (EMS) used in continuous ingot (CI) in the mechanical and metallurgical properties of hot forged flanges of AISI 1025 steel. Three conditions of raw material were supplied and compared before the forging process: one from CI using EMS; the other, prevenient from CI without EMS, and the last, with CI without EMS, and, subsequently, submitted to hot rolling process. Billets were extracted from these raw materials to manufacture connection flanges through hot forging. To evaluate the mechanical properties of the forged pieces, tension, hardness and impact tests were done, and the microstructure was observed by optical microscopy. Macrographs and penetrating liquid non-destructive testing were also done. The results of the above-mentioned tests showed proximate mechanical and metallurgical properties approved by the reference norm (ASTM A105) of the flanges manufactured with the raw materials obtained by CI with EMS and hot rolling.

Analysis of a formed metal sheet shows the data of the incremental forming process. Variation in sheet deformation results from the process and shows how forming occurred. Another important result is the surface roughness of the sheet, which reports the parameters of the process, machine and tool used. Incremental forming of the titanium CP-Ti grade 2 sheet was performed in the SPIF modality – forming without a point of support, in order to look at the thickness deformations. SPIF incremental forming is characterized as forming that does not use points of support, and therefore simple tooling is used in the process. The following resources were used to perform the practical tests: CAD/CAM software, CNC machining center, incremental die, incremental forming tool and a sheet press device. The results obtained were the finish of the formed surface, measured by the roughness parameter RZ, and the measurement of the true strains ( ) and thickness (s1). Practical tests showed that the limit wall angle ( ), for the CP Ti grade 2 sheet, 0.5 mm thick, is 47º.

The present work is focused on ferrous powder metallurgy and presents some results of a development of a suitable masteralloy for use as an additive to iron powder for the production of sintered steels. The masteralloy was produced by melting a powder mixture containing approximately Fe + 20% Ni + 20% Mn + 20% Si + 1% C (wt%), in order to obtain a cast billet that was converted into fine powder by crushing and milling. It was observed presence of SiC in the masteralloy after melting that is undesirable in the alloy. Si element should be introduced by using ferrosilicon. Sintered alloys with distinct contents of alloying elements were prepared by mixing the masteralloy powder to plain iron powder. Samples were produced by die compaction of the powder mixtures and sintering at 1200 °C in a differential dilatometer in order to record their linear dimensional behaviour during heating up and isothermal sintering, aiming at studying the sinterability of the compacts. Microstructure development during sintering was studied by SEM, XRD and microprobe analyses.

This work has the purpose of studying loudspeakers in which the cores usually constructed from cast iron or rolled metal are replaced with parts of alloy obtained from the Powder Metallurgy process. The study comprises the obtaining of hysteresis curves of pure iron and some sintered alloys such as FeP, FeNi and FeSi and simulation by the finite element considering a conventional topology of a commercial loudspeaker. The simulations include the evaluation of flow in the air gap and a theoretical study of the powers developed compared to loudspeakers with conventional cores. Keywords: powder metallurgy, simulation by the finite element, loudspeakers.

This article discusses the preliminary studies of the Single Point Incremental Forming (SPIF) process applied brass alloy Cu-35Zn, with different sheet thicknesses and formed geometries. Despite being a material widely used in industry, with excellent cold formability, there is still no relevant research on this material concerning SPIF. As a result of these preliminary studies, the necessary forces (F) during the process, the true strain (e1, e2) and maximum wall angle (ψ) supported by materials are presented and discussed.

The present work reports a comparative study of cemented carbides of compositions WC-6Co, WC-10Co, WC-20Co, WC-6Co-6Ni and WC-12Ni-6Co. The purpose was to study the powder metallurgical production process of these compositions starting from a commercial WC-6Co powder, obtaining the desired compositions by mass balance with pure Co and pure Ni powders. During the process steps mixing, milling, compacting and sintering the powders were described by its apparent density, green density, shrinkage and sintered density. Lower densities were observed in composites with higher binder content. The process was monitored by scanning electron microscopy and EDS analysis to evaluate the homogeneity of the powders, to detect contaminations by the process and to characterize the microstructure of the sintered materials. A finer microstructure was found when the binder contained Ni. Potentiodynamic polarization tests in sulfuric acid revealed pseudo-passive behavior for all the tested hard metals.

Production of small and geometrically complex parts is a typical application of powder injection molding (PIM) process. The production of parts by PIM can produce a final texture with high roughness. The roughness is an important factor of the adhesion of the human cell on the implant. This intrinsic factor can facilitate high bone - implant fixation, but it reduces the corrosion resistance of implants. A design of a temporary screw probe adapted to peculiarities of this production process was proposed to use in implants as well as in electrochemical essays. This study aims at studying the effect of surface roughness on bone attachment of titanium implants and their corrosion resistance in a saline environment. Temporary implants were produced by PIM to characterize the influence of the temperature of sintering on the self-release process of the samples. The samples were classified into three groups according to sintering temperature (1250, 1270 and 1300oC). Screws were inserted in tibiae of New Zealand white rabbits (Oryctolagus cuniculus). After 4, 8 and 12 weeks the fixation in the bone was evaluated by histomorphometry (all threads along the implant and the three best consecutive threads were analyzed). An average surface recovery of 65 % after 12 weeks of implantation was obtained. Accelerated corrosion tests point to possible susceptibility to crevice corrosion of the sintered implants. Here, we compared some of the recent patents related to corrosion behavior and biocompatibility of titanium screws produced by PIM.

The parameters for conventional powder-metallurgical production of a CoCrMo alloy for dental implants were determined. With the application of these parameters an alloy with sufficient green density, low porosity after sintering, considerable hardness and spontaneously passive behavior in the Ringer solution can be achieved. The comparison of samples with different sintering temperatures revealed that a slight variation of the sintering temperature can have a considerable effect on the physical, mechanical and electrochemical properties of the alloy.

The aim of this work is the study of sintered titanium parts for medical applications components, via process of Powder Metallurgy (M/P). This study will be a basis for the manufacture of an orthodontic interpenetrating screw. A study of constituent powders was accomplished and samples were prepared. In sequence, its physical properties were analyzed. For all alloy composition studied, the parameters of production process were respected as: compactation pressure, sintering atmosphere, and sintering time. The porosity determined by Archimedes principle was approximately 11.5%. This result is comparable to that found in the literature. The average density obtained by M/P was 4.03 g/cm3 for sintered titanium, with a density close to theoretical density of titanium, 4.5 g/cm3. Key words: powder metallurgy, sintering, orthodontic screw.

Hard metal is a composite material used in several areas of machining, mining and construction. It can be applied directly on oil and gas drilling equipment components. The main objective of this work was to apply a high energy milling technique to produce the WC-Ni composite and study the effects of milling time in the material properties. The milling of hard metal WC-20Ni, was performed for milling times of 1, 2, 4, 8, 16, 32 and 64 hours. The starting powders were characterized by laser sedigraphy, SEM and EDS. Microstrutural analysis of the sintered samples was performed by optical microscopy, microhardness and density by Archimedes. The best results for the WC-20%Ni composite were achieved for 8 hours milling, where the density and hardness reached 97.09% and 1058 ± 54 HV, respectively, after sintering.

The production of titanium parts from powder metallurgy is one of the tendencies of modern metallurgy, since it allows obtaining structures with complex geometries and controlled porosity. The purpose of this study was to produce two types of dental implant prototype, and compare them biologically. Smooth surface prototypes were obtained, by the conventional turning process and porous surface prototypes using Metal Injection Molding (MIM). The prototypes were implanted in rats that were euthanized after 3 weeks, and the bone/implant interface was analyzed. The results showed that all prototypes were clinically stable at the end of the healing period, but those produced by the MIM process presented a significantly higher percentage of osseointegration (bone/implant contact) than the milled prototypes in the same healing period. It is concluded that the bone tissue grew independent of type of implant, enabling quick, rigid fixation already in the third week of the healing process.

Cobalt based composites with tungsten carbide, titanium carbide and tantalum carbide as a hard phase dispersed finely in the cobalt matrix by mechanical alloying process in high energy ball mill have been investigated. These alloys consist in 90 wt% hard phase and cobalt as a liquid phase activator. Using liquid phase sintering at nearby 1400 °C, relative densities of 99% have been achieved, providing best wear behavior and mechanical properties by this process. It is shown that the ball milling time required for highest sintered density is heavily dependent on the milling conditions. The general advantage of this class of material is the simple and robust manufacturing process combined with superior properties.

This paper describes the behavior of 316-L stainless steel low-pressure injection molded parts, under chemical or supercritical debinding conditions. The qualitative composition of this feedstock is 316-L stainless steel powder, ethylene–vinyl acetate copolymer (EVA), 140-macrocrystalline paraffin, carnauba wax and stearic acid. Thermogravimetric analyses were used to help determine the quantitative composition of the binder system, while the quantitative composition of feedstock was determined by knowing the critical loading of the mixture. The feedstock was molded by low-pressure injection molding in an MIGL-33 machine and submitted to immersion in liquid heptane or in carbon dioxide under supercritical conditions.

Este trabajo tiene el objetivo de estudiar y analizar las propiedades mecánicas de la aleación que presenta en su composición Fe-Cu-C-Ceniza ligera obtenida por pulvimetalurgia convencional. Se determinó la densidad aparente, la curva de compresibilidad y se compactaron las muestras de los compuestos con diferentes porcentuales de ceniza. Se realizó la sinterización de las tres aleaciones generadas en atmósfera controlada por argón a temperatura de 1150°C. También se realizó ensayo de densidad, dureza y análisis micrográfico de las muestras. Analizando las propiedades presentadas, los resultados muestran que se puede utilizar la ceniza ligera en balance con la aleación Fe-Cu-C en concentración de 4,8%.

Powder forging involves axial compression of powder preforms to develop full density and to achieve the desired part shape. The process is generally carried out in a trap die consisting of a through-hole die cavity, a movable upper punch for load application and a lower punch for ejection of the part. Trap die tooling can be used because of the tight control of powder mass. In contrast, conventional forging practice uses moving die halves with flashes gutter to accommodate the variation of material mass in the starting billets. A major contribution to final properties of a powder forging is the way metal flows in reaching full density. Deformation involving extensive shearing causes collapsed pore surfaces to elongate and rub across each other, forming bonds stronger than in pores that just have collapsed with no relative surface motion or elongation. This work focus on some basic aspects in powder forging, such as characteristics, variables, advantages, and some examples of successful applications of this process. Sintered parts of Ancorsteel 4600 V steel were cold forged with different levels of deformation and subsequent heat treatments were tested. Metalographies forged densities and mechanical properties of these samples were analyzed. This paper must be understood as a contribution to the development of sintered forging as a process economically viable to the production of parts to the industry.

The production and the mechanical properties of porous parts of the biocompatible titanium alloy TiTa30 produced via powder metallurgy are described. The aim of the study was to create endosseous dental implants with a low Young's modulus and a porous surface, which will result in a good load transfer from the implant to the bone thus stimulating the formation of new bone and ultimately by the ingrowth of bone into the surface of the implant lead to a good anchorage in the bone. Other applications of such porous parts might be bearings or filters. The new alloy TiTa30 was melted in an electric-arc furnace in a water-cooled mould in an argon atmosphere and then powdered by the hydrogenation - dehydrogenation (HDH)-process. Samples were produced by unidirectional pressing and then sintering of the green bodies under vacuum. The influence of the sintering parameters (particle size, compacting pressure, sintering time and temperature) on the mechanical properties was investigated. While the Young's modulus and the yield strength varied only with the resulting porosity, the fatigue strength of the samples also depended on the particle size and the sintering temperature and time. It was possible to produce samples with a Young's modulus comparable to that of bone and a fatigue strength high enough for use as a dental implant. In addition to the mechanical testing the functionality of the implants (bone ingrowth and implant anchorage) was tested in-vivo in animal experiments.

The excellent strength/weight ratios and corrosion resistance combined with rigidity and good mechanical properties at room and moderate high temperatures lead to a wide range of application of titanium and its alloys in aerospace and non-aerospace (specially as biocompatible materials) applications. However, due to high initial cost and processing there is some limitation, mainly in critical applications where special alloys are needed. Thus, extensive investigations of more economic titaniurn powder production are in progress, in order to increase its use. Therefore, this work outlines the background of titanium powder production in order to show the better choice at dental implants.

This work introduces basic plasticity equations for the forging of sintered porous metals, presenting a model for a general state of stresses. In the simple uniaxial compression, parameters are semi-empirically determined as a function of the relative density. These parameters are introduced into equations derived for representing. Experimental results of cold forging of sintered preforms prove the validity of the present theory.

Elementary Al and Mo powder mixtures have been processed by high energy ball milling up to milling times of 100 hours. The shift of the pitting potential and the X ray analysis of green milled samples showed that part of the Mo has formed a supersaturated solid solution of Mo in Al. Elementary Mo powder, however, was still present after 100 hours of milling. Sintering led to the formation of the intermetallic Al12Mo phase.

Wind energy converters of small size used in isolated units to generate electrical energy must present low maintenance cost to such facilities economically viable. The aspect to be analyzed in cost reduction is the brake system, since in isolated systems the use of brake is more frequent reducing the brake pads life time. This study aims at analyzing the wear behavior of some materials used in brake pads. An organic material was analyzed comparing it with a commercial brake pad, and the sintered material was developed and tested. The materials behaviors were evaluated in both wear and friction coefficient. The sintered samples were made by powder metallurgy. The composition was compacted at 550 MPa and sintered in a furnace with controlled atmosphere to avoid oxidation. Despite the different compositions of the two types of materials, they presented a very similar wear; however, the sintered material presented a higher friction coefficient. An adjustment in the braking system of the wind generator might be proposed to use the sintered brake pad, due to its higher friction coefficient. Consequently, the braking action becomes lower, reducing the wear rate of the material.

This paper shows friction results obtained through compression ring tests for two commercially-available lubricants (i.e., Oildag and Deltaforge) applied in the hot forging of aluminum alloys. The experiments were performed with AA 6061 F aluminum alloy samples with the goal of observing the behavior of each lubricant in several conditions of temperature (200, 300, and 450 °C), strain rates (1, 10 and 50 s-1), and strain (25, 50 and 75%). The friction coefficients for each lubrication condition were established by means of calibration curves determined from finite element calculations with the use of the PEP/Larstran software package. An Analysis-of-Variance approach for the ring's internal diameter was followed in order to evaluate the performance of the lubricants. The results indicated that the Oildag lubricant presents a better stability as well as lower friction coefficients than the Deltaforge lubricant for the range of conditions tested, which translates into a better friction condition at die-part interface.

This study analyses the friction between a micro/meso part and a tool using the friction ring test. Four different materials were analysed, SAE1020 steel, AISI304 stainless steel, AA6531 aluminium and C34000 brass. Compression tests were performed on the four materials to determine the material flow stress curves of two different test specimen sizes and look at the size effect on the compression test. Three different ring sizes in four different materials analysed were used for the friction ring tests, applying molybdenum bisulphide-based lubrication. Based on the results of the flow stress curves, the calibration curves were performed with the SIMUFATC software for each material and size of friction ring using the Amontons-Coulomb friction model. The results of the experiments indicate a reduction in friction as the part becomes smaller, and the factor material influences the reduction of friction between the part and the tool.

This work aims at showing the feasibility of partial substitution of the machining process by hot forging, to obtain AISI 8640 steel drills bits, used to bore holes in rocks. This paper presents the tooling to obtain the piece, together with the procedure used for testing, comparing the force found in practice to computer simulation. It was found that the process proposed saved 3.5% of materials, and presented a 13% increase in piece hardness in the quenched and tempered state, compared to the piece produced conventionally.