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The aim of this paper is to study of oxidation effects in creep of the Ti-6Al-4V alloy, in different atmospheres (air, nitrogen and argon). The samples were treated during 24 hours at 600°C in different atmospheres The samples treated during 24 hours at 600°C and the oxidation behavior in each atmosphere was observed. The oxidation was more aggressive in air atmosphere, forming TiO2 film in the surface. The alloy was tested in creep at 600°C in argon, nitrogen and air atmospheres using 250 MPa. The behavior of creep curves shows that useful life is better in atmospheres not so oxidant.

This study aims to determine some mechanical properties of an Inconel 718 aged superalloy obtained through hot tensile tests. These properties as conventional 0.2% yield strength (σv), ultimate strength (σUTS), and specific elongation assessment (εu) are important parameters in the study of the mechanical material behavior. The superalloy was subjected to hot tensile tests at 650 to 700°C and a strain rate of 0.5 mm/min according to ASTM E-8. It is used a scanning electron microscope (SEM) to obtain images of the fracture surface of the specimens. The images of the fracture surface are analyzed in order to relate the temperature of the test with the type of mechanism of fracture.

The automotive industry has identified several automobile components that could be replaced with titanium alloy components, either through direct replacement in existing designs or, preferably, in new designs to fully exploit the unique properties of titanium. The alloy processing by powder metallurgy (M/P) eases the obtainment of parts with complex geometry and, probably, cheaper. In this work, results of the Ti-35Zr-10Nb alloy production are presented. This alloy due to its high wear, impact and corrosion resistance is a promising candidate for automotive applications. Samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering between 900-1400 °C, in vacuum. Sintering behavior was studied by means of dilatometry. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively.

In the present work we study the static indentation, i.e., the formation of small dents which result from laboratory tests specifically developed with this purpose. A mathematical model will be presented. It is based on the numerical and experimental tests performed with previous adjustment of all the mechanical variables involved. This model considers the test specimen and indentator geometry, the sheet anisotropic condition, the sheet's plasticity, and the contact conditions between the plate and the indentator developed. There is a goal to satisfy: specific requirements of a consumer market which is continuously willing for the development of materials with thinner thickness and better mechanical properties. To reach this goal, high strength steels manufactured by the SCAL (Sheet Continuous Annealing Line) are already been produced and tested in experimental scale. These bake-hardening steels can be used to manufacture external panels in the automobile industry.

In this work five methods of heat treatments are investigated in order to obtained convenient volume fractions of ferrite, bainite, martensite and retained austenite, starting with a low carbon steel and seeking the distinction of the phases, through optical microscopy. Specific chemical etching is improved. The results in tensile and fatigue tests were accomplished and the results were related with the microstructural parameters. The results show that the mechanical properties are closely related with the phases, grains size and the phases morphology.

The aim of this paper is to analyze the microstructural development in samples of Ti-48Al-2Cr-2Nb (at.%) alloys obtained by powder metallurgy (P/M). This alloy has potential applications when high operating temperatures are required, e. g. turbines, aerospace applications, automotive engines valves and turbocharger rotors. The elementary powders were mixed for 1 hour, cold uniaxially pressed at 60 MPa and sintered at 1100°C, for 1 hour, under vacuum. Then, the specimens were milled and submitted to a second stage that included cold isostatic pressing (400 MPa) with subsequent hot uniaxial pressing (20 MPa), between 900 up to 1200°C, for 2 hours, in argon atmosphere. The alloys were characterized by XRD (X-ray diffraction), SEM (Scanning Electron Microscopy), EDS (Energy Dispersive Spectroscopy) and Vickers microhardness measurements. The results indicated the viability of the route and the tendency of a lamellar microstructure in high sintering temperatures.

The present study concerns laser surface nitriding of Ti-6Al-4V. The Ti-6Al-4V alloy was submitted a superficial treatment of pulsed laser Nd:YAG (λ=1.064 μ\m) in atmosphere of 40wt% nitrogen-60wt% argon. The samples were characterized by optical microscopy and electron scanning microscopy. The microstructure of the surface nitrided Ti-6Al-4V consists of TiN dendrites distributed in α--Ti matrix. It can be noted that there is a significant enhancement in surface roughness after surface nitriding (6.60 μm) as compared to the as received Ti-6Al-4V (0.46 μm). The microhardness of the surface is improved to 1100 VHN as compared to the 340 VHN of substrate.

The diamond thin films chemical vapor deposition (CVD) on sintered tungsten carbide (WC-Co) tools shows increasing interest in the technological research, due to rapid growing utilization of aluminum alloys, like Al-Si alloys, in the automotive industry. Sintered carbides, mainly diamond coated sintered carbides, are very suitable to machine aluminum alloys. The cobalt binder that accounts for the WC-Co substrate toughness degrades the interface film-substrate, catalyzing the formation of graphite preferentially to diamond during the deposition process. In addition, stresses are generated in the interface between WC-Co substrate and deposited diamond film due to thermal expansion mismatch. These two factors are a technological neck to large-scale production of diamond CVD coatings for machining tools. In this work, several interface pre-treatments were developed and applied resulting in high film-substrate adherence, adequate for machining tool purposes.

Search for alloys with improved high temperature specific strength and creep resistance properties for aerospace applications has led in the last decades to sustained research activities to develop new alloys and/or improve existing ones. The maraging steels evoked tremendous interest, especially in the aerospace world. Extra low carbon, high nickel, iron based alloys held great promise of providing an extraordinary combination of structural strength and fracture toughness. Applications of this alloy include aircraft structural components and rocket engine case for Satellite Launcher Vehicles. The objective of this work is to study the creep behavior of a solution treated Maraging 300 alloy. Constant load creep tests were conducted with this alloy at 550°C and in a stress range of 200 to 500 MPa. The creep parameters are determined. Samples with a gage length of 18.5 mm and a diameter of 3.0 mm were used for all tests.

The study of creep has a major importance when materials are submitted to high stress and homologous temperature. Superalloys are designed to operate under high stress, temperature and corrosion environment. Those properties of superalloys are due to high temperature stable matrix, solid solution elements and precipitated particles. This study aims to determine the creep resistance of Inconel 718 aged superalloy obtained through the tests according to ASTM E139-06, at stress range of 510 to 700 MPa and temperature of 675°C. The parameters as the primary creep time (tp), steady-state creep rate (εs), time to rupture (tr) and strain to rupture (εr) are important to evaluate the creep resistance. It used a scanning electron microscope (SEM) to obtain images of the fracture surface of specimens. The images of the fracture surface were investigated in order to relate the temperature of test with the fracture mechanism.

Materials with appropriate behavior at high temperatures and aggressive environments have become a scientific and technological necessity nowadays. Studies have been undertaken for improvement in getting new alloys, especially for the reevaluation of existing commercial alloys, through the acquisition of data under conditions of higher severity. In this context it was used for this work to Ti-6Al-4V in the form of cylindrical bars, provided forged and annealed at 190°C for 6 hours and cooled in air, which has favorable properties for aerospace application. The alloy after heat treatments to obtain the bimodal structures, martensite and Widmanstätten was subjected to creep tests at 600°C under the conditions of 250 and 319 MPa, in the form of constant load. The structures of Widmanstätten and martensite showed higher creep resistance in both stress conditions used in the trials.

CVD diamond film deposition on WC-Co substrate is the most likely application of diamond CVD technology towards large scale production, due to its suitability to aluminium alloys machining in the automotive and aerospace industry. Several film-substrate interfaces and surface modifications have been developed aiming higher levels of simultaneous diamond film-substrate adherence and substrate surface toughness, however the results are still far bellow industry requirements for widen scale application. In this work a new interface is introduced in the CVD diamond films technology, which consists of a thermo-reactive deposited and diffused vanadium carbide layer, highly adequate to diamond films deposition on cemented carbide cutting and forming tools. This interface presents good diamond growth characteristics, thermal expansion coefficient similar to the substrate and, in addition, high hardness and mechanical strength.