30 research outputs found
Tribological behavior ol ABNT 1020 and ABNT 1045 steels bubmitted to solids thermochemical treatments
No full textThe interest for improvements in tribological properties of materials, more specifically in steels with low and medium carbon content are of great importance for mechanical components life time. In this work, thermochemical treatments were carried out on ABNT 1020 and ABNT 1045 steels, in order to compare and evaluate the tribological behavior and also the phases and layers formed, to the different types of treatments which are: boronizing, nitriding and multi component boronizing (also known as duplex treatment). The specific objectives were to plan the different ways of treatment; evaluate and compare the effect of the substrate according to the microstructure, support and interface of the layers formed through the treatments; characterize the wear mechanisms for the different treatments and compare the results of both materials. The thermochemical treatments were carried out, using as basis previous works performed by the powder metallurgy research group. Boronizing and nitriding treatments were carried out by solid means, multi component boronizing treatment was performed in two ways: in the first one, boronizing was followed by nitriding (BN) and the in the second one, nitriding was followed by boronizing (NB). These duplex treatments were performed with the same conditions of time and temperature used for nitriding and boronizing treatments. Pin-on-disk sliding wear tests were performed using WC-Co (hard metal) balls as counter body. Through the test it was possible to evaluate the tribological behaviour. Friction coefficient, volume of removed material and wear mechanisms were determined. The microhardness of the formed layers was measured at the surface and on the cross section of the specimens. X-ray diffraction was used to confirm the formed compounds on nitriding, boronizing and boron-nitriding (duplex) treatments. The results showed an increase in the hardness of the surface layer and a reduction in the amount of removed material (volume) in all thermochemical treatments comparing with the condition of non-treated samples. Regarding the tribological behavior, by evaluating the thermochemically treated samples, the nitrided samples of ABNT 1020 presented the highest amount of removed material (0,078 mm3) and its hardness was 436 HV0.05. The boronized ABNT 1020 steel presented the lower amount of removed material (0,013 mm3). The boronized ABNT 1045 steel reached the highest mean hardness on the surface (1750 HV0.05) and the NB duplex treatment in this material provided the highest hardness of the formed layer, about 2270 HV0.05.O interesse por melhorias nas propriedades tribológicas de materiais, mais específico em aços com baixo e médio teor de carbono são de grande importância para a vida útil de componentes mecânicos. Neste trabalho foram realizados diversos tratamentos termoquímicos em aços ABNT 1020 e ABNT 1045, com o objetivo de comparar e avaliar o comportamento tribológico e também as fases e camadas formadas, para as diferentes formas de tratamentos que são: boretação, nitretação e boretação multicomponente (também conhecido como tratamento duplex). Os objetivos específicos foram: planejar as formas de tratamentos; avaliar e comparar o efeito do substrato relacionado à microestrutura, ao suporte e interface das camadas formadas nos tratamentos realizados; caracterizar os mecanismos e formas de desgastes para os diversos tratamentos e comparar entre os dois materiais. Os tratamentos termoquímicos foram realizados, utilizando como base trabalhos anteriores que foram realizados no grupo de pesquisa de metalurgia do pó. Os tratamentos de boretação e nitretação foram realizados por via sólida, o tratamento de boretação multicomponente foi realizado de duas formas: na primeira foi realizada a boretação seguido de nitretação (BN) e a segunda foi a nitretação seguido de boretação (NB), nos tratamentos duplex utilizaram-se os mesmos parâmetros de boretação e nitretação. Foram realizados ensaios de desgaste por deslizamento do tipo pino sobre disco, com esferas de WC-Co (metal duro) como contra corpo. Foram avaliados: o coeficiente de atrito, o volume de material removido e os mecanismos de desgaste. A dureza da camada formada foi avaliada por microdureza na superfície e na seção transversal. Difratometria de raios-X foi utilizada para a comprovação da formação das camadas de nitretos, boretos e boro-nitretos (duplex). Os resultados mostraram melhoras principalmente na dureza da camada superficial e redução no volume de material removido, em todos os tratamentos termoquímicos, quando comparado com amostras sem tratamento. Em relação ao comportamento tribológico, avaliando as amostras tratadas termoquimicamente, as amostras nitretadas do aço ABNT 1020 foram as que apresentaram os piores resultados com volume de material removido de 0,078 mm3 e dureza de 436 HV0,05. Já a boretação no aço ABNT 1020 foi o tratamento que apresentou o melhor desempenho em volume de material removido com 0,013 mm3. O aço ABNT 1045 com tratamento de boretação apresentou a maior dureza média na superfície, com 1750 HV0,05 e o tratamento duplex NB neste mesmo material proporcionou a maior dureza na seção transversal, resultante da camada formada de nitretos-boro com 2270 HV0,05.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio
Study of tribological behavior of AISI H13 steel subjected to boriding thermochemical treatment
No full textIn this work, solid boriding thermochemical treatment was carried out using Ekabor® 1-V2 and one blend as boriding agents and heat treatment of quenching and tempering of AISI H13 tool steel in order to compare and evaluate the tribological behavior and the properties acquired for four studied conditions, that were: Ekabor® powder boriding, Ekabor® powder boriding followed by quenching and tempering, boriding with a blend as boriding agent and quenched and tempered condition. Sliding wear tests were performed in pin-on-disc apparatus in order to evaluate the friction coefficient and the volume of material removed (measured with the aid of a profiling equipment). After the wear tests the samples were transversally cut for metallographic evaluation by optical and scanning electron microscopy. X-ray diffraction was used to confirm the formation of borided layer. The results showed that the boriding treatments, regardless the boriding agent used, are effective in increasing wear resistance. The thickness of borided layer was greater for boriding with Ekabor® powder than the blend agent, this one, nevertheless, showed significant improvement in wear resistance compared to the quenched and tempered condition. There are several wear mechanisms that take place in the sliding wear test but the adhesive wear mechanism was reduced by boriding treatment.Neste trabalho foram realizados tratamentos termoquímicos de boretação por via sólida com pó comercial Ekabor® 1-V2 e mistura boretante, além de tratamentos térmicos de têmpera e revenimento em aço ferramenta AISI H13 com o intuito de comparar e avaliar o comportamento tribológico e as propriedades adquiridas para quatro condições estudadas, sendo elas: boretação com pó Ekabor®, boretação com pó Ekabor® seguida de têmpera e revenimento, boretação com uma mistura como agente boretante e condição apenas temperada e revenida. Testes de desgaste por deslizamento foram realizados em tribômetro de pino-sobre-disco para avaliação do coeficiente de atrito e volume de material removido (avaliado com o auxílio de perfilômetro). Após os ensaios de desgaste as amostras foram cortadas transversalmente para avaliação metalográfica através de microscopia óptica, microscopia eletrônica de varredura e microdureza. Os mecanismos de desgaste foram analisados por microscopia eletrônica de varredura. Difratometria de raios-X foi utilizada para a comprovação da formação da camada de boretos. Os resultados mostraram que o tratamento de boretação, independentemente do agente boretante utilizado, é eficaz no aumento da resistência ao desgaste. A espessura das camadas de boretos foi maior para boretação realizada com pó Ekabor® em comparação com a mistura boretante, esta última, apesar disto, apresentou melhoria significativa em comparação com a condição de têmpera e revenimento. Vários são os mecanismos de desgaste que ocorrem no ensaio por deslizamento sendo que o mecanismo de desgaste por adesão foi reduzido com a realização dos tratamentos de boretação.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio
Materiales compuestos de matriz metálica. II parte. Métodos de procesado y consolidación de MMCs reforzados con partículas
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Multi-component boron and niobium coating on M2 high speed steel processed by powder metallurgy
No full textA multi-component boron and niobium coating can improve properties compared to conventional boron coating. A thicker layer of boron diffusion could be formed, providing a support layer of higher mechanical strength for the hard layer. The objective of this research is to develop a boron and niobium-based coating on the high-speed steel M2 produced by powder metallurgy (P/M). Firstly, calculations by ThermoCalc® were made to estimate parameters of niobium boronizing. Secondly, thermochemical treatments by pack cementation were carried out, in stages and also simultaneously. Microstructures, phases, hardness, roughness, wear resistance and coefficient of friction of the coatings were investigated. Finally, coatings composed of niobium carbides or niobium borides and iron borides, measuring more than 3000 HV0.025 of hardness was obtained by niobium‑boron based treatments. However, the best wear resistance was conferred in the boronizing coating.The authors would like to acknowledge financial support to the Ph.D. student from FAPESC, under the studentship number 0951801-0-01, from CAPES for Sandwich Doctorate, BEX 9676/11-2. Also, they would like to thank the UC3M and UDESC universities, where this investigation was performed
Influence of boriding treatment on the mechanical properties of Monel 400
No full textThe Monel 400 nickel-copper alloy exhibits high corrosion resistance but low wear resistance. The boriding thermochemical treatment aims to improve wear resistance by increasing the surface of the material hardness. Previous studies on boriding Monel 400 and other nickel alloys, using boriding powder containing iron and silicon and high treatment temperatures, indicate that these factors may promote material oxidation and reduce the thickness of the nickel boride layer. In this study, a powder composed of 90 wt% B4C and 10 wt% KBF4 was used to boride Monel 400 samples at three different temperatures and treatment times, resulting in varying layer thicknesses. Microstructural characterization was conducted using confocal microscopy, microhardness testing, Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). X-ray Diffraction (XRD) was used to determine the phases present. The boron activation energy, determined through kinetic diffusion theory, was found to be 157.2 kJ mol−1. To validate the experimental results, predicted layer thicknesses based on activation energy were compared with experimental boride layer thicknesses from validation samples. The comparison revealed a standard deviation of 11.80% for samples treated at 825 °C for 3 h and 18.65% for samples treated at 875 °C for 3 h. Additionally, instrumented indentation analysis was performed on each sample. A more comprehensive study was conducted on samples treated at 850 °C for 4 h, which included mapping of hardness and Young's Modulus from the layer region to the substrate. This analysis revealed the formation of distinct regions: (I) nickel borided region, (II) diffusion of borides at the grain boundaries, and (III) substrate. Furthermore, copper agglomeration was observed between regions (I) and (II)
INFLUENCE OF TiO2 ADDITION IN ALUMINUM ALLOYS
No full text<p>This work verifies the influence of high-energy milling processing in the fabrication of an aluminum metal matrix composite reinforced with TiO2 nanoparticles. The base alloy (AA2014) was produced by high-energy milling and subsequently the reinforcement was added. After obtaining the base alloy and the composite, the powders were compacted in a uniaxial cylindrical matrix with a compression tension of 490 MPa, and then the material was extruded at 490° C.</p>
AVALIAÇÃO DE DUREZA POR TRATAMENTOS TÉRMICOS DO COMPÓSITO AA2014-5%TIO2 PRODUZIDO POR METALURGIA DO PÓ
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