Metal matrix composites (MMCs) are relatively new materials on science and materials engineering. In this work was used single-walled carbon nanotube (SWNT) as reinforcement in an aluminum matrix. For this purpose, 0.75% (by weight) of SWNT was dispersed with isopropanol using ultrasonication and mixed with particles of aluminum powder. The samples with and without SWNT were dried and compacted at room temperature with a pressure of 400 MPa for obtain a billet with 4,8x4,8x25,0 mm3. These compacted billet were subjected to Equal-Channel Angular Extrusion - ECAE (Φ=90 °) at room temperature. The influence of the presence of SWNT, of the number of extrusion passes (0, 1, and 3 passes), of the extrusion route (A or BC) and of the use of back pressure (0-65 MPa) in densification and hardness of the composite was evaluated. Optical microscopy was used to characterize the morphology of the aluminum grains, the dispersion of SWCNT and present pores in the samples. The results indicated that the density and hardness of the samples are increased with the increase in the number of extrusion passes and the use of back pressure. The microstructures showed alignment of the aluminum grains and of the CNT clusters in a direction close to the shear imposed by the ECAE process and increase of the dispersion because of the necking and defragmentation of the CNT clusters.

One of the problems encountered in heat exchangers working at high temperatures is the degradation caused by erosive processes, especially in coal-fired power plants. One of the factors that contribute to the degradation of the material is the microstructural changes, like the spheroidization of the carbides. This reduces the mechanical strength of the material and consequently accelerates its wear process. The objective of this work was to evaluate the effect of spheroidization under erosive wear conditions on ASTM A106 steel. The samples were submitted to different treatment times and temperatures, aiming to generate spheroidization in the samples, later submitted to erosive wear tests. Loss of mass, microstructures and mechanical strength were evaluated from the microhardness, with the evolution of the spheroidization process. The samples with higher level of spheroidization, obtained in the temperatures of 730 ° C in times above 50 hours presented greater reduction of hardness that resulted in greater losses of mass. In general, with the increase of spheroidization, there is reduction of mechanical resistance and erosive erosion, but with a gradual reduction in wear rate. This is possibly due to the increased ductility / toughness of the matrix, which delays the process of debris formation on the ASTM A106 steel surface during the hot erosive process.

ResumoA utilização de materiais resistentes a corrosão, e em substituição a materiais agredidos por agentes corrosivos, vem tomando proporções mundiais no setor industrial, alimentício e offshore, desde que estes possuam as mesmas características mecânicas dos materiais substituídos. O objetivo deste trabalho é abordar as relações existentes entre parâmetros de usinagem, geometria de ferramentas com a integridade superficial do aço inoxidável AISI 316L no processo de torneamento. Os testes realizados em torno CNC usando variações nos parâmetros de velocidade de corte e avanço da ferramenta. Enquanto no que diz respeito as ferramentas, foram variadas as dimensões dos raios de ponta dos insertos intercambiáveis, bem como a ausência de qualquer agente lubrirefrigerante. Onde, para cada condição foi realizada a medição da rugosidade média e a dureza do núcleo da amostra usinada e sua superfície, fazendo, posteriormente o comparativo dos testes. Foi verificado que o raio de ponta da ferramenta e o avanço tem uma maior influência na rugosidade superficial, enquanto a velocidade de corte não apresentou uma influência significativa. Os resultados também indicam que há uma variação de dureza da superfície usinada em relação ao núcleo das amostras, entretanto, cada condição indica diferentes valores de dureza, o que demostra que a variação dos parâmetros de corte também altera a integridade superficial de peças submetidas ao processo de usinagem. Palavras-chave: Parâmetros de Usinagem. Torneamento. Acabamento. Rugosidade. Aço AISI 316 L AbstractThe use of materials resistant to corrosion, and in substitution of materials attacked by corrosive agentes, has been taking on worldwide proportions in the industrial, food and offshore sectors, as long as these have the same mechanical characteristics as the replaced materials. The aim of this pape ris to address the existing relations between machining parameters, tool geometry and the surface integrity of AISI 316 L stainless steel in the turning process. The tests performed on the CNC lathe using variations in the cutting speed and tool feed parameters. While with regard to the tools, the dimensions of the tip radius of the interchangeable inserts were varied, as well as the absence of any lubricant coolant. Where, for each condition, the measurement of the average roughness of the core of the machined sample and its surface was performed, subsequently making the comparison of the tests. It was verified that the tool tip radius and the feed have a greater influence on the surface roughness, while the cutting speed did not have a significant influence. The results also indicate that there is a variation in the hardness of the machined surface in relation to the core of the samples, however, each condition indicates diferente values of hardness, which shows that the variation in cutting parameters also changes the surface integrity of parts submitted to the machining process. Keywords: Machining parameters. Turning. Finish. Roughness. AISI 316 L steel.