Thin films of titanium aluminum nitride (Ti(1-x)AlxN) were deposited on silicon, copper, and plasma nitrided AISI D2 tool steel substrates through reactive direct current grid-assisted magnetron sputtering. The depositions were performed in the metal and compound modes using nitrogen flow rates of (7.2 ± 0.1) sccm and (6.8 ± 0.2) sccm, respectively. The relations between the process parameters and the crystallographic orientation were investigated. Chemical and mechanical properties were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and instrumented indentation technique (IIT). X-ray diffraction spectra and electron diffraction patterns revealed the presence of a Ti(1-x)AlxN phase with a face-centered cubic structure in both films. In metal mode, the coatings exhibited a preferential (111) plane orientation, changing to (200) in the compound mode. The change in preferential orientation was influenced by the reactive gas partial pressure.

The Montmorillonite-Erucamide nanocomposite (MMT-EU) can be used to reduce and to control the values of coefficient of friction of low-density polyethylene films (LDPE), widely used by the food industry. In this work, the effect of the addition of 5 wt% and 10 wt% of MMT-EU on the mechanical properties of LLDPE films involving the weld region was investigated. The MMT-EU concentration range was defined considering its possible technological application as an additive to stabilize the friction coefficient of polymeric films. The result shows a significant improvement in the values of stiffness, strength and ductility of polymeric films. In addition, it did not change the coefficient of friction, but the brightness of the LLDPE films decreased and the opacity increased, due to the increase in the crystallinity degree of the LLDPE polymer promoted by MMT-EU, not being a problem for the application of these films.

Stainless steels have been evaluated in the form of coatings or thin films deposited using magnetron sputtering in various investigations. In most of these investigations, mainly the microstructural evaluation of this type of coating has been reported, while the evaluation of wear resistance has not been widely studied. In the present investigation, ferritic-austenitic stainless steel coatings with different percentages of silver were deposited by means of unbalanced DC magnetron sputtering. A stainless steel target doped with different numbers of silver inserts (0, 1, 2, 3, and 4 inserts) was used, obtaining coatings with silver percentages of up to 7.7 at. %, in order to evaluate their tribological properties. During the synthesis, the first layer of the bilayer was deposited with argon and the other in an atmosphere of argon and nitrogen. The structure of the coatings was evaluated by use of X-ray diffraction (XRD), and the morphology and the chemical composition were studied by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. The hardness was tested through nanoindentation, and the wear test was carried out using the pin-on-disc technique. The wear tracks were evaluated via profilometry, SEM, and EDS. In general, the deposited films exhibited BCC and FCC phases and a compact morphology, as well as good adherence to the substrate. The results of the evaluation of the mechanical properties revealed an increase in the hardness of the coatings when the silver content was augmented, obtaining values of 9.8 GPa and 12.1 GPa for coatings with 0 and 4 silver inserts, respectively. Likewise, it was found that the wear resistance of coatings was higher, up to two orders of magnitude compared to the 316L stainless steel substrate. Finally, the wear rate of the multilayers decreased slightly with an increase in the percentage of silver in the films produced, up to an order of magnitude for the coating with 4 silver inserts relative to the coating with 0 silver inserts.

ABSTRACT In this work, titanium nitride (TiN) and titanium aluminum nitride (TiAIN) films have been obtained via triode magnetron sputtering. The films were deposited using a direct current source on plasma nitrided AISI D2 tool steel (duplex treatment), non-nitrided steel, and silicon. The nitrided layer was characterized by scanning electron microscopy (SEM), Vickers microhardness, and X-ray diffraction (XRD). The films were characterized by SEM and XRD. The mechanical properties of the coatings were determined using the instrumented indentation technique (IIT) and the adhesion of the film to the substrate was qualitatively evaluated using the Rockwell C test. Both films presented no significant variation in hardness (H) and elastic modulus (E). However, compared to the films obtained in non-nitrided steel, the duplex treatment improvided the film-substrate adhesion. The improvement in adhesion can be attributed to the preliminary plasma nitriding treatment and the compressive loads acting on the nitrided surface.

RESUMO O processo de recobrimento por pulverização catódica é uma técnica amplamente utilizada para produção de revestimentos metálicos e cerâmicos, devido a versatilidade no controle das propriedades com pequenas mudanças nos parâmetros de processo, como densidade de potência aplica ao cátodo magnetron e atmosfera de trabalho. Sendo assim, as propriedades mecânicas dos filmes que estão altamente relacionadas à estrutura cristalina e composição química podem ser controladas, tornando o processo viável para aplicações nas mais diversas áreas. Utilizando-se um alvo de aço inoxidável AISI 316 foram depositados filmes com quatro valores diferentes de densidade de potência aplicada ao cátodo e com três porcentagens diferentes de N2 na atmosfera de deposição. O objetivo é determinar a influência destes parâmetros na estabilização das fases alfa e gama com estrutura cristalina cúbica de corpo centrado (CCC) e cúbica de face centrada (CFC), respectivamente. Os filmes obtidos foram caracterizados por difração de raios X, medida da espessura por microscopia confocal, dureza e módulo de Young por indentação instrumentada. Os resultados mostram que as variações da densidade de potência aplicada ao cátodo resultam em filmes com estrutura CCC com dureza e módulo de Young de 10,0 GPa e 210 GPa, respectivamente. Alterando-se a porcentagem de N2 na atmosfera de deposição obteve-se filmes formados pela mistura das fases alfa e gama, com dureza e módulo de Young de 7,5 GPa e 166 GPa, respectivamente.

ABSTRACT The coating process using magnetron sputtering technique is widely used to create metal and ceramic coatings, due to the versatility on the control of the properties just adjusting few variables of process. Therefore, the properties of metallic coatings, which are connected with the crystalline structure and chemical composition, can be controlled, so the process could be used in a lot of areas of interest. Thin films were deposited using a stainless steel AISI 316 target in four different power densities applied to the cathode and in three different N2 percentages in the work atmosphere. The objective is to understand the influence of these parameters on phase stabilizing of alpha and gamma that have body centered cubic (BCC) and face centered cubic (FCC), respectively. The deposited thin film was characterized by X-ray diffraction, thickness, hardness and Young’s modulus. The results shown that changing the density power applied to the target result in thin films with CCC structure, hardness and Young’s modulus of 10,0 GPa and 210 GPa, respectively. Changing the percentage of N2 on the work atmosphere the thin films grow with alpha and gamma phase with hardness and Young’s modulus of 7,5 GPa and 166 GPa, respectively.

RESUMO Filmes de polietileno de alta densidade (PEAD) foram tratados por plasma radiofrequência (RF) de N2/O2. Foi investigado o efeito da pressão do gás de trabalho N2/O2, do plasma, na texturização superficial do filme. O plasma gerado em baixa potência (20W) permite manter a amostra em baixa temperatura (T<40°C) durante o tratamento de superfície. Os resultados mostram que a rugosidade superficial, em escala nanométrica, é muito sensível à pressão do gás de trabalho, entre 0,01Torr e 0,5Torr. Quando o material é tratado em pressão mais baixa (0,01Torr), observa-se a formação de uma estrutura superficial nanométrica de vales e picos com elevada regularidade. Por outro lado, quando o tratamento é feito em pressão mais alta (0,5 Torr), observa-se a formação de uma textura mais grossa na superfície da amostra, além da formação de ilhas de moléculas oxidadas. Em todos as condições estudadas, as amostras tornaram-se hidrofílicas após o tratamento por plasma, mantendo a característica de hidrofilicidade durante vários dias após o tratamento, retornando gradativamente à condição original de molhabilidade.

ABSTRACT HDPE films were treated in the post-discharge region of N2/O2 plasma, powered by a radio frequency power supply. Therefore, in this paper, it was investigated the role of pressure in molding the nano-topography of the polymer. The treatment was carried out in low temperature (T <40 ° C) and time of 5.0 min, in order to preserve the integrity of the polymer bulk. It is well known that the production and recombination rate of reactive species in the plasma depends on the working gas pressure. Results show that the surface nano-roughness is very sensitive to pressure, between 0.01Torr and 0.5Torr, making it possible to use as a fine control parameter for polymer nano-texturing. In the lower pressure treatment it was observed regular nano-peaks and nano-troughs on the surface of the sample. Contact angle measurements show that, in general, the surface becomes hydrophilic after N2/O2 plasma treatment. In addition, samples treated in higher pressure generate oxidized islands by the action of the oxidizing plasma. All samples became more hydrophilic after plasma treatment, maintaining this hydrophilicity characteristic for several days.

RESUMO A nitretação por plasma é um tratamento termoquímico que modifica as propriedades superficiais de um determinado material. Este processo aplicado em aços ferramenta resulta no aumento da dureza da superfície através da formação da zona de difusão pelo controle das variáveis de tratamento, tais como a temperatura, composição química da atmosfera de trabalho e tempo de tratamento. Neste trabalho discute-se um procedimento alternativo para o tratamento térmico de revenimento. O qual possibilita a redução nos custos de fabricação, diminuição no consumo de energia e no tempo de confecção das ferramentas. Amostras de aço ferramenta VF 800 AT foram temperadas e revenidas (três vezes) pelo tratamento térmico convencional com posterior nitretação por plasma. Em cinco outros grupos de amostras realizou-se o revenimento concomitantemente ao tratamento de nitretação. A superfície e o núcleo das amostras foram caracterizados por difração de raios x, microscopia ótica, microscopia eletrônica de varredura, microdureza Vickers e dureza Rockwell C. Os resultados mostram que o gradiente térmico entre a superfície e o núcleo das amostras afeta a microestrutura, a dureza e as fases obtidas durante o tratamento térmico de revenimento simultâneo à nitretação. Entretanto, quando dois revenimentos são realizados em forno tipo Mufla e o último tratamento ocorre simultaneamente à nitretação, obtêm-se microestruturas, fases, dureza e microdureza semelhantes ao ciclo de tratamento térmico convencional com posterior nitretação por plasma.

ABSTRACT Plasma nitriding of tool steels improves the surface hardness due to formation of diffusion zone and/or compound layer. The process parameters such as temperature, gas composition and dwell time, allow us to control the layer thickness, the microstructure, the crystalline phases and the type of layer (for example white layer or diffusion zone). This paper discusses an alternative procedure for the heat treatment of tempering and surface treatment, both in plasma or combining conventional heat treatment with subsequent plasma nitriding. Carring out both treatments in plasma could enable reduction in manufacturing costs, lower energy consumption and less time for tools manufacturing. Samples of VF800AT steel were treated and characterized (at surface and core of samples) through the following technique: X-ray diffraction, optical microscopy, scanning electron microscopy, micro-hardness profile and Rockwell C measurement. Temperature measurements during the plasma treatment, show that arise thermal gradient between the surface and the core of the samples. In this work, it was observed that the surface was up to 7% hotter than the core of sample, during the plasma treatment with temperature of magnitude about 5 x 102 °C. This thermal gradient seems inherent to the plasma process, so that it can produce different microstructure, hardness and crystalline phases between core and edge of samples. However, when two tempering operations are prior carried out in a muffle furnace and the third tempering treatment is subsequently carried out simultaneously with the plasma nitriding, it is observed that the microstructure, the crystalline phases, hardness and micro hardness (in both, edge and core) are similar to treatments done in conventional mode cycle (in muffle furnace) with subsequent plasma nitriding.

This paper reports the effect of pulsed bias in comparison with DC bias on reactive deposition of Ti6Al4V-N films, obtained by Grid Assisted Magnetron Sputtering. The results obtained by X-Ray diffraction (XRD), Energy Dispersive X-ray Fluorescence Spectrometer (EDX) and Atomic Force Microscopy (AFM) show that bias condition affects the crystalline texture and change the roughness and morphology of the films. The DC bias favors the film crystallinity, however the pulsed bias produces smoother films.

In the present work, the electrochemical behavior of WC-CoCr coatings with 10 (W10), 15 (W15) and 20 (W20) torch passes sprayed by High Velocity Oxygen-Fuel (HVOF) flame on AA7050 aluminum alloy substrate, evaluated in 3.5% NaCl solution, were compared using open-circuit potential (E OC) measurements, electrochemical impedance spectroscopy (EIS) and polarization curves. The coating surfaces and their cross sections were characterized by X ray diffraction and the Rockwell-C hardness test, and also by optical (OM) and scanning electron microscopy (SEM) before and after the corrosion tests. The electrochemical data showed that sample W10 presented higher corrosion resistance than the others in chloride solutions. In some tests, aluminum salts on the coating surface were identified by EDS, indicating the corrosion of the substrate. And using aluminon, aluminum ions were detected and analyzing the surface via stereomicroscopy, hydrogen bubbles were observed, both showing that the electrolyte reached the substrate and galvanic corrosion possibly occurred. The physical characterization showed that sample W10 presented a lower number of cracks and pores, justifying its higher corrosion resistance.