Currently, machining has been the process of metal-mechanical transformation of great importance and use, demanding several developments of technologies that aim at better efficiency of operations. As technology advances, consumers demand products with better cost/benefit, which in machining, impact on cutting tools with longer life, or in reducing operating costs such as the use of cutting fluids. However, in some cases, special needs outweigh these requirements, such as the presence of cutting oil in products from the oil/gas sector, making it important to search for techniques that can replace emulsions and increase tool life. In this sense, this work analyzed the use of the air-cooled system in the internal turning of a product from the oil and gas sector, compared with the use of emulsion and dry cutting. For this, the responses of forces in the cut, roughness and cylindricity in cutting conditions similar to those used in the industrial environment were evaluated. The results showed that, although the use of emulsion provides better responses, in some cases, there is improvement in the cutting forces with the replacement of the air cooled system. But, there was a worsening in the geometric deviation responses, roughness and cylindricity, due to the air flow.

Superalloys are widely used in high temperature applications and harsh environments. Inconel 625 is one of the most applied superalloys due to its high resistance to oxidation and mechanical properties. In this work, the microstructure and oxidation mechanism at 900 and 1000 °C of the Inconel 625 superalloy manufactured by the directed energy deposition (DED) and conventionally manufactured (CNV) additive manufacturing process were studied. The samples were cyclically oxidized for up to 100 cycles and isothermally oxidized at 900 °C for 200 hours and at 1000 °C for 100h. Each thermal cycle consisted of 60 minutes at the oxidation temperature and 10 minutes in which the samples were exposed to room temperature for cooling. To characterize the oxidized layers, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analyzes were carried out. The microstructure of the DED samples alternated between fine equiaxed grains and columnar grains, with Nb and Mo segregations located in the dendritic and interdendritic regions. At 900 °C the oxidation rate was similar for both materials, both in the cyclic and isothermal tests, but was clearly higher for the DED material at 1000 °C in both tests. Inconel 625 (CNV and DED) showed detachment at 900 and 1000 oC in cyclic tests. The oxide layer was identified as predominantly Cr2O3 under all conditions, providing good resistance to oxidation. In addition, oxides such as NbCrO4 as well as NiCr2O4 were identified for the CNV and DED samples. In isothermal tests, the delta phase Ni3(Nb,Mo) was observed for the CNV and DED alloys at the grain boundaries at 900 °C and at the metal/oxide interface for both temperatures as a result of chromium depletion. Finally, Inconel 625 produced by DED showed lower resistance to oxidation, being related to the microstructure, the segregation and the open porosity observed in the samples produced by DED.

Sustainability is one goal for all industrial process nowadays. The great challenge is to have more and more cleaned and optimized processes. Considering the negative impact of mineral or vegetal coolant on the environment and operator health, the target of this study was to provide an alternative cooling method with cold air to replace the liquid coolant. In advanced process with high cutting speeds, the function of cooling the cutting region is much more important than lubrication. To analyze the differences between the cooling methods, tests were performed using vegetal coolant, as traditional method and cold air in two different conditions, with the air flow directed to the rake surface and also directing the air to the rake surface and flank surface. The temperatures, cutting forces and average surface roughness (Ra) were measured as responses and ANOVA was used as method of analysis. The preliminary results indicate that there are no significant differences in cutting forces and surface roughness, but the cold air didn’t have the same or better cooling efficiency. New tests including liquid nitrogen will be performed in an attempt to improve the cooling efficiency keeping in the way of clean cooling methods, mainly because the results for cutting forces and surface finishing were satisfactory.

The helical milling process has been explored in the production of holes for various industries,
standing out biomedical and aerospace. Due to the high precision required and the difficulty of
machining the titanium alloy Ti-6Al-4V, the cutting parameters need to be defined in order to obtain
acceptable levels of quality and precision for such applications. Helical milling, when compared to
conventional drilling, is recommended because it presents low levels of cutting forces and better
quality due to the kinematics of the process. In this work, the main objective was to study the helical
milling to obtain holes in the titanium alloy Ti-6Al-4V. For this purpose, a Box Behnken Design
(BBD) planning was used, enabling the obtaining of second-order regression models capable of
optimization, as a function of the cutting parameters of helical milling, being them, the axial and
tangential feeds per tooth and the cutting speed. The average roughness Ra, circularity (Ront) and
material removal rate (MRR) responses were evaluated. The models obtained for the Ra and Ront
analysis presented adjustments of 87.99% and 84.92% successively, corroborating a good
proportion of explanation of the data variability, having sufficient reliability for a greater
evaluation of the effects of the variables on the responses presented. Finally, for optimization, the
multiobjective optimization method by adaptive geometry estimation (AGE-MOEA) was used to
determine a set of Pareto optimal solutions for the finishing response and the material removal rate.
According to the optimization, to minimize roughness and circularity, it is necessary to adopt as
feeds: fza = 0.71 µm/tooth and fzt = 0.06 mm/tooth and a cutting speed: vc = 59.16 mm/min, while
for greater productivity, it is necessary: fza = 1.20 µm/tooth and fzt = 0.07 mm/tooth and a cutting
speed: vc = 59,16 mm/min. As analyzed through scanning electron microscopy (SEM) images, it
was possible to conclude that for low fza levels, combined with a low cutting speed, inferior surface
quality was observed due to the dragging and adhesion of removed material, as a consequence of
the difficulty in evacuating the chip.

Currently, austenitic stainless steels are produced in large quantities, possessing good mechanical properties, including high toughness and cold workability, with nickel as the primary phase stabilizer. For economic reasons, however, some alloys use manganese as a partial or total substitute for nickel, such as FeMnSiCrNi, which offer relatively low cost, good workability, and ease of processing. Nevertheless, at high temperatures, manganese preferentially reacts with oxygen rather than chromium, preventing the formation of a protective Cr2O3 layer; furthermore, Cr2O3 tends to volatilize at higher temperatures, thus compromising the alloy's oxidation resistance. In contrast to chromium oxide, alumina (Al2O3) is more stable under such conditions; however, the amount of aluminum required to form a protective layer would result in unacceptable mechanical properties. This study evaluated the effect of a coating obtained by pack aluminizing on the oxidation resistance of an FeMnSiCrNi alloy. Cyclic and isothermal oxidation tests were conducted at temperatures of 900 and 1000 °C. At 900 °C, the coating significantly improved the alloy’s oxidation resistance, delaying degradation due to spallation. In the isothermal regime, the aluminized samples showed no spallation; despite manganese diffusion the aluminized coating remained intact. At 1000 °C, however, both aluminized and non-aluminized samples presented loss of mass under both cyclic and isothermal conditions. Compared to other studies, although, the aluminized alloys oxidized at 900 °C achieved significantly better results, given that the tests were conducted under more severe conditions of regime and temperature.

Threads are fastening elements of great importance in the assembly of mechanical components. The mechanical industry uses thread profiles and standardized diameters to assemble machines, parts of devices, and other equipment. Among the standard metric thread diameters, M6, M8, and M10 are the main ones, with the M8 diameter being the most used. Therefore, the objective of this work was to measure and compare the maximum tensile load supported by M6x1.00mm internal threads in an aluminum alloy AA 7075-T6, with 1, 3, and 5 threads fillets, manufactured by the  machining and forming processes. Screws with 12.9 grade were used to analyse the tensile strength of threads with a displacement speed of 1 mm/min and the dimensions of the specimens with an external diameter of 22 mm and thickness of 2.00 and 3.00 mm. After the tests and the necessary analyses, it can be observed that the machined threads presented more excellent resistance in aluminum AA 7075-T6. On the other hand, the threads manufactured by the conventional drilling process for opening machined and rolled threads showed the highest strengths in the tensile tests. In addition, it can be concluded that the screw used was able to withstand the stresses applied to the thread in AA 7075-T6 aluminum machined and laminated with 5 thread fillets. 

This study evaluates the mechanical properties of polyester and polyurethane matrix composites based on castor oil, reinforced with different mass fractions (5% and 15%) of silicon carbide (SiC) grains with different sizes (37µm and 53µm) and shapes (sub-angular and angular) through a complete factorial analysis of 2¹4¹ order. 

This work compares the behaviour between epoxy and novel biobased castor oil matrix composites reinforced with glass and aramid fibres and manufactured by Resin Transfer Moulding (RTM) assisted by vacuum-infusion. A full factorial design (2² - DoE) is applied to statistically identify the effects of the factors, polymer and fibre type, on the tensile, flexural, and impact properties of these composites. The results follow a normal distribution and homogeneity of variances, validating the DoE. Both main factors affect tensile properties. Aramid fibre composites subjected to tensile loads improve by 76% their mechanical performance compared to the glass fibres case, while the epoxy matrix shows a superior behaviour (up to 39%) to the biobased castor oil polymer composites. The epoxy systems provide an increase of up to 46% of the flexural properties; in contrast, the type of fibre used is not statistically significant. The main factors and their interaction significantly affect the impact energy properties, and glass fibre-reinforced castor oil composites have 78% more impact resistance than the other combinations. Finally, the low bulk density of the castor oil polymer combined with aramid fibres however provides equivalent or superior specific performance to other composites that offer adequate absolute properties for secondary structural applications.

Natural fibres have some advantages over synthetic fibers, such as low density, high tenacity, biodegradability, reduced respiratory irritation, flexibility, and low cost, thus being a cellulosic fibre with satisfactory mechanical properties for use as reinforcement in polymeric materials. This work focuses on the use of banana fibres as reinforcing members, exploring the use of castor oil-derived polyurethane resin as a matrix phase. Among the parameters that can be controlled, are the length (10 mm and 30 mm), the grammage (0.0375 g/cm² and 0.0750 g/cm²) of the fibre; the fibre extraction process; and the alkaline treatment with sodium bicarbonate (NaHCO3). The potential use of this biodegradable composite was evaluated by its performance in mechanical tests of tensile and flexural strength. The analysis of the results (using DOE and ANOVA) considered the isolated parameters and the interaction between them in the physical and mechanical properties of the composite. It was observed that the fibre length, when considered alone in the first experimental analysis, impacts the flexural strength, even when considered in combination with the fibre weight. The composite reinforced by banana fibres showed much improved mechanical properties compared to the pure matrix, with the 30 mm fibre showing better behavior compared to the 10 mm fibre, and with a higher grammage. The fibre extraction process revealed composites with different mechanical properties, highlighting higher-weight composites with fibres from the first extraction process. Alkaline treatment, when combined with fibre weight, impacts the mechanical properties, generating less dense composites. Composites of greater weight and without alkaline treatment showed better results. Alkaline treatment on banana fibres was not effective. The composites manufactured with the first batch of fibres - larger size, and heavier weight - presented higher structural performance.

Crash-Test is a vehicle impact test that aims to analyze and evaluate a vehicle's ability to withstand different types of crash. During a collision, most of the impact energy is absorbed by the vehicle's structural elements in order to offer the greatest possible protection to the occupants. In addition to the test with the impact of the actual vehicle, simulation analysis using the Finite Element Method (FEM) is used. In this way, the FEM plays an important role in the analysis of the vehicle's impact resistance, reducing development time and project costs. Most of the structural components of the vehicle body are manufactured by the stamping process. This manufacturing process imposes a plastic deformation on the parts along with a distribution of non-uniform thickness, residual stresses, and strain hardening of the grains, especially in high strength and high ductility steels. 3D Scanners s are devices used to generate digital representations of real-world objects or environments. They can be used to evaluate possible geometry distortions arising from the manufacturing process. The 3D model of the component is obtained by measuring the distance from various points on the object's surface to a fixed point in space. In this study, the influence of the manufacturing process for three (03) different types of loading was analyzed: a quasi-static compression test at 5 mm/s of a crash box in order to calibrate the collapse load; a second test with a part of the main structure of the vehicle at 16 km/h and finally a test carried out in an isolated Origami crash box in an drop tower with 162 kg at a speed of 24 km/h. Then, the numerical simulation results will be compared with physical tests performed in the laboratory. The mapping of plastic strain and thickness variation had a significant influence on the correlation of the crash box collapse load as well as on the collapse mode in relation to the physical test. Scanning the crash box Origami after manufacturing showed a big difference in geometry when compared to original CAD and had a significant influence on the collapse mode correlation.

Sustainable machining methods have been developed to reduce or replace the fluids used in cutting metal in the industry. Several processes, such the minimum quantity lubrication (MQL) for example, have shown promising results in relation to the surface finish and the reduction of machining efforts, temperature, friction and tool wear. They also have high performance with high-speed cutting and when working with difficult-to-machine materials such as titanium and their alloys, characterized by its high strength, high melting point and low thermal conductivity, in addition to its wide application in several areas of engineering. Recent studies seek to improve its use also in the production of biomedical implants due to its low elastic modulus, corrosion resistance and its biocompatibility, without posing risks to human health. The finite element method together with the experimental tests allowed the evaluation of the influence of the fluid in different temperature conditions in relation to dry machining in the microcut process of commercially pure titanium specimens, Grade 2. The results pointed to the best dry machining performance. The temperatures adopted for the fluid did not present significant differences between them, or any characteristic that justified its use. The effects of the high pressure of the fluid injection pump were responsible for the increase in the friction coefficient, the machining forces and the specific cutting energy.

High temperature oxidation processes occur in different types of machines and equipment in the most varied fields of activities, in which stainless steels are used. Therefore, it is important to study and characterize the oxide layers formed and the mass variations that occur during the oxidation of these materials. Ferritic matrix stainless steels appear as a lower cost alternative to austenitic steels for high temperature applications. In this way, the present work will present an analysis of the isothermal and cyclic oxidation in high temperature of the ferritic stainless steel AISI 439. Studies have shown that the initial surface finish of the sample can have an important effect on the oxidation kinetics and on the adhesion of the oxide film. Therefore, in order to evaluate the effect of roughness on the behavior of the oxidation kinetics of this alloy, two different surface finishes were used. Half of the samples were sanded with silicon carbide sandpaper to #600 granulometry and the other half remained with a factory surface finish (laminate) on the faces. The isothermal and cyclic oxidation tests were carried out at temperatures of 750, 850 and 950 °C, in a time interval of up to 100 hours or cycles. The thermal cycles consisted of heating and holding for 1 hour at maximum temperature, followed by cooling for 10 minutes. The microstructure and chemical composition of the oxide layers formed were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray Diffraction (XRD). The alloy showed parabolic oxidation kinetics at the three test temperatures for the two surface finishes evaluated, which indicates the presence of an oxide film with protective characteristics. However, the surface with greater roughness (laminate) showed less tendency to detachment. The oxides Cr₂O₃, TiO₂ and MnCr₂O₄ were identified in the XRD analyzes for the two surface conditions evaluated.

Iron-based austenitic FeMnSiCrNi alloys, with shape-memory properties, are potentially cheaper alternatives to conventional austenitic stainless steels. However, the high manganese content reduces their high-temperature oxidation resistance. Manganese has a high affinity with oxygen and, in high temperatures, reacts with it, forming the oxide layer, which depletes the metallic substrate and forms ferritic structure in the oxide/metal interface region. Previous studies have shown several effects of this ferritic layer in physical and chemical properties of FeMnSiCrNi alloys, but there is limited information regarding the characterization of this layer and the mechanisms by which it is formed. In the present study, the alloys Fe-13,67Mn-3,46Si-8,32Cr-3,04Ni (A) and Fe-13,04Mn-3,77Si-9,56Cr-3,55Ni (B) were studied via cyclic oxidation tests at 800 °C and isothermal oxidation tests in temperatures between 675 and 1000 °C. The oxidation behavior and subsurface ferritic layers were evaluated by mass change analysis, as well as X-Ray Diffraction (DRX), Scanning Electron Microscopy (SEM), optical microscopy and Energy-dispersive X-ray spectroscopy (EDS) techniques. Alloy A was less resistant to oxidation, except at 700 °C, temperature at which alloy B presented higher mass gain, associated with the stabilization of ferrite at the oxidation temperature. The relationship between mass gain and ferritic layer thickness was linear. A mechanism by which the ferritic layer forms during cooling was proposed via analysis of manganese concentration gradients. In cyclic tests, the ferritic layer was thinner and more depleted in manganese, due to the formation of ferrite between cycles, inducing a chemical effect that consumes part of the substrate. Isothermal tests with varying cooling rates (by oven, air or water) showed that ferrite is formed, at least partially, at the oxidation temperature. The exception is at 1000 °C, temperature at which ferrite seems to form Only upon cooling.

Alumina is an advanced ceramic used as a biomaterial due to properties such as biocompatibility, high compressive strength, good chemical inertia in the physiological environment, among other good characteristics. Scaffolds are structures with pores of various sizes, well distributed and interconnected, thus favoring the adhesion of cells and the growth of tissue inside the pores. The biomimetic method was used for coating alumina scaffolds with calcium phosphate in order to improve bioactivity. The method presents advantages to low cost, reproducibility and applicability to the complex surface and porous structures. The study objective was to manufacture the porous alumina samples coated with calcium phosphate by biomimetic method for use as bioceramic scaffolds. The dense alumina samples were uniaxially compacted under pressures of 50, 100, 150, 200 and 250 MPa and sintered at 1500°C for 120 minutes. The pressure was determined experimentally to produce the scaffolds. The porous alumina samples using ammonium bicarbonate (BA) as a pore forming agent were uniaxially compacted at a pressure of 200 MPa with 30 wt.%, 40 wt.% and 50 wt.% BA, heat treated at 270°C for 120 minutes for removal BA and sintered at 1500°C for 120 minutes. Then, it was possible to determinate that porosity of 55% was obtained with 40 wt.% BA. The scaffolds were compacted at 200 MPa with 40 wt.% BA and 60 wt.% alumina, heat treated at 270°C for 120 minutes and sintered at 1500°C for 120 minutes. The samples were biomimetic coated submerging in a Simplified Solution (SS) of calcium chloride dehydrate (CaCl2.2H2O) and sodium hydrogen phosphate dehydrate (Na2HPO4.2H2O) for periods of 14 and 21 days. Analysis of laser particle size distribution was realized, Scanning Electron Microscopy (SEM), density and porosity using geometric and Archimedean methods, Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), Fourier-transform infrared (FTIR). The scaffolds had a porosity of 55%, with good distribution, interconnection and varying pores sizes. Calcium phosphate formation was observed in the scaffolds on both surface and pores after 21 days on biomimetic coating. The samples presented promising results to be used as scaffold.

Global competition encourages manufacturing companies to overcome technical and commercial challenges that provide competitive advantages and positively impact the sustainability of their processes. In this context, the mechanical forming processes appear as a viable alternative in terms of efficiency, compared to other transformation processes. The deep drawing process consists of mechanically forming a blank into a final format specified by the project. This blank is forced against a die by a punch that usually has the internal shape of the finished part. In this research, the influence of the punch geometry and the type of lubricant on deep drawing by the Swift test was evaluated. There are few researches related to the influence of punch geometry. As for lubrication, the possibility of replacing mineral oils with vegetable oils impacts sustainability criteria because they are biodegradable, are easy to dispose of and do not affect the health of professionals. Cups formed from a steel-PVC-steel sandwich material were stamped using punches without grooves and with grooves. The lubricants were Renoform mineral oil and linseed and castor oil of vegetable origin. The analyzed responses were the maximum stamping force and roughness in the Ra, Rz and Rt profiles. It was found that the type of punch had a greater influence on the maximum stamping force, with a reduction occurring when the punch with grooves was used. The reduction in the maximum stamping force results in greater energy efficiency, minimizes friction forces, reduces press load among other advantages. When analyzing roughness, only the type of lubricant exerted influence. The study showed the possibility of replacing mineral lubricant with vegetable oils in some cases.

Avaliação da resistência à corrosão na indústria química do revestimento com Nb₂O₅ aplicado por aspersão térmica.

Studies show that porous titanium alloys promote osteointegration at the implant-bone interface improving the mechanical stability. However, researches on bioactive coatings that induce the formation of new bone tissue on the surface of metal implants have been gaining prominence, being calcium phosphate (CaP) coatings of great potential. In this work, samples of Ti35Nb were produced by powder metallurgy and coated with calcium phosphate (CaP) by biomimetic method, for use in orthopedic or dental implants. High purity titanium and niobium powders were mixed and uniaxially compacted. For fabrication of macroporous samples, a pore former additive was added in the mixture (Ammonium Bicarbonate – AB). The sintering of samples was performed at 1300 ºC for 2 h in an ASTRO furnace under argon atmosphere. The samples underwent a chemicalthermal treatment for bioactivate the surface by means of the formation of a sodium titanate interlayer. Then, the samples were immersed in a simplified biomimetic solution with ionic CaP-forming composition, for periods of 14 and 21 days. The samples were characterized in terms of density and porosity, as well as chemical, physical and mechanical analyzes were performed by SEM / EDS, SEM / FEG, XRD, RAMAN, XPS, SEM / FIB, TEM, Profilometry and Ultra Microhardness. In general, the formation of micro and macroporous Ti-β alloys were observed. The deposited coatings were identified as biocompatible hydroxyapatite phase. According to the literature hydroxyapatite is the most desired phase for implants application because it presents chemical composition closer to the bone.

The use of composite materials has been growing in various industrial sectors. Sandwich panels are structural composites with high flexural rigidity and low weight, consisting of faces, core and adhesive. Honeycomb cores composed of circular or tubular cells have been shown to be superior to hexagonal cells in terms of energy absorption under deformation, flexural strength and structural rigidity. On the other hand, there is currently a great debate about the amount of solid waste generated by the population worldwide, mainly polymeric waste. In this context, the present work proposes the direct use of polyvinyl chloride (PVC) tubes for the manufacture of sandwich panels with ISO 1200 aluminum faces. It is investigated the effects of the outside diameter of the tube (20 and 32 mm), type of packing (cubic and orthotropic) and type of connection between tubes (with or without mechanical interlocking) on the physical and mechanical properties of panels subjected to three-point bending. The properties are evaluated statistically through Analysis of Variance (ANOVA). The panels with orthotropic packing, 32 mm tubes and without interlocking present a better mechanical performance in relation to other conditions. Interlocking is not an efficient strategy due to the large increase in the density of the structure. The viability of using PVC pipes to fabricate sandwich panels is shown in this study, being a sustainable and economical alternative use of these solid residues from civil construction.

The lubrication is an important parameter for the success or failure of a deep drawing operation. The formulation of traditional lubricants uses mineral oils, which are harmful to the operator's health and difficult to discard. Recent studies have proved the lubricating potential of vegetable oils in deep drawing, and seek for solid additives that can complement the properties of these base oils. The deep drawing of a composite material is highly applicable for the metal industry, meeting the multifunctional needs that steels cannot satisfy. The current work presents an experimental study using vegetable oils with silica micro particles in the deep drawing process of a composite in a sandwich arrangement, formed by a SAE 1006 steel blank, an electrolytic copper blank and a thin PVC inner layer. For the lubrication, were chosen the castor, cotton and canola oils, two samples of silica of different particle sizes, and three different concentrations 1, 3 and 5%. As a final product of the deep drawing, a cup with an internal diameter of 22 mm and a height of 10 mm was shaped. The effect of the lubrication on the deep drawing process was evaluated by the maximum stamping force and the surface finish of the cup, by the roughness parameters Ra and Rz measured on the side and bottom of the cup. The studied composite showed consistency with other materials for stamping. The maximum force values corresponded to previous studies, influenced only by the different types of silica. The influence of the lubrication on the roughness was observed only on the side of the cup. The best surface finish was obtained with the silica of greater granulometry, and sub-angular geometry, using the oils of castor and cotton, and by the addition of silica in lower proportions.

Reis, R. A., (2020). Study of the behavior of conventional and niobium-modified MAR- M246 superalloy cyclically oxidized at 900 and 1.000 ºC. Dissertation (Master Degree) – Universidade Federal de São João Del Rei, 2020.

The oxidation process consists of the reaction of metal alloys with gaseous atmospheres forming an oxide layer on the material surface. At the industrial processes, there are a series of engineering components exposed to oxidation (among them those made with nickel- based superalloys) with temperature changes, different heating and cooling rates and different frequencies. It configures the cyclic oxidation process. Therefore, this research aims to carry out a comparative study of conventional MAR-M246 superalloys, and, also, the same alloy, with tantalum replaced by niobium, to evaluate the formation of oxidized layers in cyclic oxidation tests and characterize them. To test, it was used an oven with an automated system, with cycles of 1 hour of heating and maintenance at high temperature and 10 minutes of cooling in air. The samples were tested for 120, 180 and 240 thermal cycles at 900 ºC and for 24, 120 and 180 at 1,000 ºC. To characterize the oxidized layers, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X- Ray Spectroscopy (EDS) were performed. The tests results at 900 ºC showed mass gains very close to both alloys, with the superalloy MAR-M246 modified with niobium it was showed slightly higher mass gain. In tests at 1,000 ºC, sulfur contamination in the atmosphere was detected, which became the environment more degrading, causing failure of the stainless steel support. However, even so, the two alloys proved to be quite resistant, with greater stability for the alloy containing niobium. Protective oxides, Cr₂O₃ and Al₂O₃ were identified in all test conditions, as well as TiO₂, NiO and Ni(Co)Cr₂O₄. Internal oxidation of Al₂O₃ was identified at both test temperatures, but in greater amounts in samples oxidized at 900 ºC and, at this temperature, the modified MAR-M246 superalloy appeared to have less internal oxidation. It was noticed that the two superalloys had a very similar behavior in terms of mass gain, along with the oxidized layers. This fact suggests an advantage of using niobium for applications with cyclic oxidation at a temperature of 900 ºC due to its lower density and cost. The advantage in the use of niobium could not be affirmed for the temperature of 1.000 ºC due to the sulfur contamination of the cyclic oxidation oven, however, suggested a good behavior for both alloys in sulphidizing environments.

The forming process is must used by industries and consists of changing the shape and dimensions of the material through the application of external mechanical stresses. The main forming processes are rolling, drawing, extrusion, forging and sheet forming. The sheet forming process can be divided into stretching, bending, deep drawing and cutting. Stamping is widely used in the automotive and white-line industries. However, for the stamping to occur the use of lubricants is preponderant. On the other hand, the stamping process causes structural modifications and on the surface of the product, such as alteration of the roughness, the tightness of the wall and the presence of residual stresses. Although the stamping process is used in several sectors, the literature on lubrication of stamped products with solid particles and the influence of lubrication on the residual stress of the material is very scarce. In this work was analyzed the influence of the lubrication in the process of cold stamping of ABNT 1010 and 1020 steels in the generation of residual stress and the surface quality of a product. The blank were stamped without lubricant, mineral lubricant and vegetable lubricant with polyethylene terephthalate particles. Hardness and roughness tests were performed in the samples to verify surface finish and the insertion of residual stresses of compressive or tensile stresses were generated on the material. The results showed that the lubrication generated compression stresses on the stamped parts. The best lubrication relative to microhardness was found in linseed oil with PET particles between 150-300 μm. Regarding surface finish, the best lubricants were vegetable oils combined with PET particles smaller than 150 μm and cotton with particles between 300-600 μm. In addition, numerical simulation was performed by the Deform program to compare the residual stresses obtained in the simulation with the experimental results. The simulation results did not converge with the experimental method. It is assumed that this divergence is due to the use of the coefficient of friction formula in this work.

COMPARAÇÃO DO DESEMPENHO DE FERRAMENTAS DE CERÂMICA NO FACEAMENTO DE FERRO FUNDIDO NODULAR NO ESTADO ENDURECIDO