Abstract To improve the wear resistance of cutting tools made of high-speed steel, the Diamond-Like Carbon (DLC) coating appears as a promising alternative. There are several methods to assess wear, however, it is a challenge for manufacturing engineering to work with thin films, due to the uncertainty in the boundary of the substrate and the coating. Based on this concern, this study proposed the evaluation of the tribological behavior of the DLC coating deposited on AISI M35 steel, seeking to predict its behavior in machining conditions based on characterizations, nano-indentation, micro-abrasion and ball-on-disc test. Results showed that the DLC coating produced for this study consists mainly of sp2 hybridizations. The results of the nano-indentation showed that DLC coating may have a better wear resistance when compared to high-speed steel, and the nano-hardness and Young's modulus do not necessarily obey a positive correlation. Compared to high-speed steel, DLC provided reductions of 71% and 69% without micro-abrasive wear and without friction coefficient during sliding, respectively.

RESUMO Peças fabricadas com polímeros de alto desempenho têm sido substituídas por materiais similares, sendo produzidas com uma composição de polipropileno (PP), que tem um custo mais baixo. Uma das composições mais comumente utilizadas é a junção do polipropileno com fibras, resultando na formação de um novo material, com características diferentes às dos seus constituintes. Este tipo de junção é denominado compósito. O objetivo deste trabalho é avaliar o comportamento do compósito de polipropileno com fibra de vidro para a substituição do material da carcaça de um elemento filtrante fabricado atualmente com um compósito de nylon e fibra de vidro na proporção de 30% em peso. Foram injetados corpos de prova usando PP puro e com cargas de fibra de vidro nas proporções de 15%, 20% e 30%, a análise de comportamento, através de ensaio de tração, flexão, resistência ao impacto, dureza, índice de fluidez e determinação do índice de contração indicou o compósito PP com 30% de fibra de vidro com melhor comportamento. Posteriormente realizou-se a injeção da carcaça do elemento filtrante no compósito PP com 30% de fibra de vidro que passou por testes práticos.

ABSTRACT Parts made from high performance polymers have been replaced by similar materials, produced with a polypropylene (PP) composition, with a lower cost. One of the most commonly used compositions is made by the the joining of polypropylene with fibers, resulting in a new product with different characteristics from those of its constituents. This type of joint is called composite. The objective of this study is to evaluate the behavior of the fiberglass polypropylene composite for the replacement of the housing material of a filter element which is currently manufactured with a nylon and glass fiber composite in the proportion of 30% by weight. Test specimens was injected by using PP pure and as well as with 15%, 20% and 30% fiberglass loads, for behavior analysis through tensile test, flexural strength, impact strength, hardness, flow index and determination of contraction rate. After the injection in the composite with best behavior, PP 30% fiberglass, the filter element housing was subjected practical tests.

Although the 6150 steel has an excellent fatigue and impact resistance, it is unsuitable to operate it when the corrosion is a limited factor. We propose here a sequence of steel pre-treatment by carburizing, carbonitriding and nitriding in order to improve the poor adhesion between Diamond Like-Carbon coatings on steel. This sequence is our attempt to reduce the difference between the coefficients of thermal expansion of steel and DLC through the graded interface. This work demonstrates the quantitative analysis of the molecules present at surface using X-ray photoelectron spectroscopy. The crystallographic structures are investigated by X-ray diffraction which shows the formation of carbides and nitride phases. Raman spectroscopy reveals the carburizing surface characteristics where DLC coating is nucleated and grown at the substrate. At the end of the analysis it is possible to verify which molecules and phases are formed on the steel surface interface after each step of pre-treatment.