In this paper, the influence of gas nitriding (80% H2-20% N2) pressure (between 3 and 7 Torr) on the modification of surface properties of AISI 316L stainless steel is examined. The structural, mechanical, tribological and electrochemical properties of the layer produced in disk samples were studied. The samples’ characteristics were determined by scanning electron microscopy, X-ray diffraction, electrochemical potential curves, microhardness, roughness and wear tests. When pressure increases, the microhardness, elasticity and thickness also increase. The maximum thickness of the nitrided layer was 6.4 µm, the hardness reached 2200 HV0.0036 and the mass loss decreased until 1% relatively to the unnitrided sample. The X-ray diffractograms showed the presence of the expanded austenite in all the samples. The correlation between these diffractograms and the corrosion results corroborate to the most recent previous conclusions of our systematic study, which evince the interconnection between the improvement of the corrosion resistance and the presence of nitrides on the top of the nitrided layer. More significant presence of such nitrides was observed for the sample nitrided at 6 Torr, whose corrosion performance was better than for the other samples. This pressure seems to be the most indicated to improve the properties under study. Moreover, the results verified not only that the sample geometry is an important factor for enhancing these properties but also that the border effect, which causes the rings on the disk border, depends on the pressure, but not on temperature or time from the plasma nitriding process.

A cada dia o avanço tecnológico nos leva a encruzilhadas como a construção de veículos mais leves, com menor consumo de combustível e mais seguros. Neste sentido, materiais compósitos poliméricos são materiais usados atualmente em diferentes aplicações nas quais a leveza combinada com um alto módulo de elasticidade são características importantes. Poliamidas reforçadas com fibras de vidro se apresentam como materiais de grande futuro em aplicações automotivas. Desta forma, torna-se importante o estudo do comportamento deste tipo de material quando submetidos a processos de usinagem. Dentre os processos de usinagem o processo de furação é um dos mais utilizados nos componentes de material compósito. Neste trabalho será analisada a influência do avanço, da velocidade de corte e da geometria da ferramenta na força de avanço, pressão específica de corte e desvios dimensionais do furo realizado. Os testes foram realizados em poliamida sem reforço (PA6) e reforçada com 30% fibra de vidro (PA66-GF30) utilizando brocas de carbonetos sinterizados (K20) com ângulos de ponta diferente. Os resultados apontam claramente para a melhor usinabilidade do material reforçado em comparação ao sem reforço.

The continuous technological advance has led to the challenge of building lighter and safer vehicles, but with lower fuel consumption. Within this scenario, polymeric composites are materials currently used in different applications, where lightweight combined with high modulus of elasticity are important features. Polyamide reinforced with glass fiber face a promising future for automotive applications, thus becoming important to study the behavior of this type of material when subjected to machining processes. Among the machining processes, drilling is one of the most widely applied to composite materials. In this work the influence of feed rate, cutting speed and tool geometry on thrust force, specific cutting pressure and hole dimensional deviations is investigated. The tests were performed on unreinforced polyamide (PA6) and on polyamide reinforced with 30 wt % glass fiber (PA66-GF30) using tungsten carbide drills (K20) with different tip angles. The results clearly indicate the superior machinability of the reinforced material, compared with the unreinforced polyamide.

The miniaturization of components and systems is advancing steadily in many areas of engineering. Consequently, micro-machining is becoming an important manufacture technology due to the increasing demand for miniaturized products in recent years. Precision machining aims the production of advanced components with high dimensional accuracy and acceptable surface integrity. This work presents an experimental study based on Merchant and Lee & Shaffer theories applied to precision radial turning of AISI D2 cold work tool and AISI 1045 medium carbon steels with uncoated carbide tools ISO grade K15. The aim of this study is to evaluate the influence of feed rate on chip compression ratio (Rc), chip deformation (ε), friction angle (ρ), shear angle (Φ), normal stress (σ) and shear stress (•) for both work materials. The results indicated that the shear angle decreased and chip deformation increased as the chip compression ratio was elevated without significant differences between both materials. Additionally, higher cutting and thrust forces and normal and shear stresses were observed for the tool steel. Finally, the Lee & Shaffer model gave shear plane angle values closer to the experimental data.