RESUMO A crescente necessidade de aumentar a produtividade do setor industrial, impulsiona o desenvolvimento de novos aços e novos tratamentos que possam melhorar o desempenho e a vida útil de ferramentas de corte, conformação e estampagem. Tratamentos de superfície assistidos por plasma destacam-se nesse contexto. Trabalhos anteriores têm demonstrado que esses revestimentos são eficientes no aumento da dureza, na resistência ao desgaste e na resistência a corrosão de diversos tipos de aços. Nesse sentido, amostras e ferramentas de aços AISI M2 e D2 termicamente tratadas foram submetidas aos processos de nitretação a plasma convencional, em gaiola catódica e tratamento duplex com o objetivo de avaliar o efeito desses tratamentos em ferramentas de conformação buscando a viabilidade da aplicação do método no setor industrial com a redução do custo de fabricação na conformação e estampagem de pregos. Ensaios de microdureza Vickers, análise por MEV e Difração de Raios-X (DRX) possibilitaram identificar propriedades mecânicas, camada de compostos e as fases presentes, respectivamente. O desempenho das ferramentas baseou-se na quantidade de pregos produzida em kg. O custo produtivo foi determinado em função da produtividade, do preço de aquisição da ferramenta e do preço da nitretação. O uso da nitretação a plasma se mostrou viável para os dois aços, destacando-se o fato de que as ferramentas de aço D2 nitretadas a 480ºC por 3 horas, obtiveram os maiores ganhos de produtividade em relação a ferramenta não nitretada. A aplicação da nitretação convencional na ferramenta de aço M2 a 480ºC por 4 horas possibilitou a redução de seu custo em 26% e redução de 3,5% sobre o custo total de produção de pregos, obtendo o melhor custo-benefício.

ABSTRACT The growing need to increase the productivity of the industrial sector, drives the development of new steels and new treatments that can improve the performance and useful life of cutting, forming and stamping tools. Plasma-assisted surface treatments stand out in this context. Previous research has shown that these coatings are efficient in increasing hardness, wear resistance and corrosion resistance of different types of steels. In this sense, samples and tools from AISI M2 and D2 heat-treated steels were subjected to conventional plasma nitriding processes, in cathodic cage and duplex treatment in order to evaluate the effect of these treatments on forming tools seeking the viability of applying the method in the industrial sector with the reduction of the manufacturing cost in the conformation and stamping of nails. Vickers microhardness tests, SEM analysis and X-Ray Diffraction (XRD) made it possible to identify mechanical properties, layer of compounds and the phases present, respectively. The performance of the tools was based on the volume of nails produced in kg. The productive cost was determined in function of productivity, the purchase price of the tool and the nitriding price. The use of plasma nitriding proved to be feasible for both steels, highlighting the fact that the D2 steel tools nitrided at 480ºC for 3 hours, obtained the greatest productivity gains in relation to non-nitrided tool. The application of conventional nitriding in the steel tool M2 at 480ºC for 4 hours made it possible to reduce its cost by 26% and reduce by 3.5% the total cost of producing nails, obtaining the best cost-benefit ratio.

In this study, the numerical analysis of instrumented indentation testing was combined with the experimental procedure to evaluate the mechanical properties and thickness of a titanium nitride (TiN) film deposited on titanium substrate (Ti) by plasma processing. TiN film thickness is an important parameter for the surface treatment industry. In numerical analysis, the finite elements method (FEM) was applied using Marc™ commercial software. Initially, the mechanical properties of the film and substrate were determined using a numerical-experimental methodology, combining the results of indentation testing with a Berkovich indenter and the same numerical simulation for both the film and substrate. Next, the behavior of instrumented Vickers hardness as a function of maximum indenter penetration depth (hmax) was compared with the numerical results of this hardness as a function of the ratio between penetration depth and film thickness (hmax/t). Both curves were fitted using power law equations, which calculated film thickness applying a new convergence algorithm. Finally, it also was shown that the film thickness obtained agrees with the experimental range reported in the literature.

In recent decades, changes in the surface properties of materials have been used to improve their tribology characteristics. However, this improvement depends on the process, treatment time and, essentially, the thickness of this surface film layer. Physical vapor deposition (PVD) has been used to increase the surface hardness of metallic materials. The aim of the present study was to propose a numerical-experimental method to assess the thickness (l) of films deposited by PVD. To reach this objective, Vickers experimental hardness data (HV) assays were combined with numerical simulation to study the behavior of this property as a function of maximum penetration depth of the indenter (hmax) into the film/substrate conjugate. A strategy was developed to combine the numerical results of the H x hmax/l curve with Vickers experimental hardness data (HV). This methodology was applied to a TiN-coated M2 tool steel conjugate. The mechanical properties of the studied materials were also determined. The thickness results calculated for this conjugate were compatible with their experimental data.