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OLIVEIRA, V. M. C. A. Study of the Creep Phenomenon on Ti-6Al-4V Alloy Subjected to Treatments of Plasma Nitriding and Carburizing. 2010. 118 p. Dissertation (Master of Science) Escola de Engenharia de Lorena, Universidade de São Paulo, Lorena, 2010. This work aims to evaluate the effect of plasma nitriding and carburizing on the Ti-6Al-4V alloy subjected to creep in the range 500-600 °C. The results showed that the microstructure of Ti-6Al-4V consists of Widmanstätten morphologie, with a hardness of 300 ± 17 HV for the as received condition and 334 ± 18 HV for the sample heat-treated. After treatments thermochemical by plasma was observed for plasma nitriding the formation of a nitrided layer of hardness of 1539 ± 157 HV and of average thickness of 4 μm. The hardness is due to the thickness and the presence of Ti2N and TiN phases identified by X-ray diffraction. For plasma carburizing was observed the formation of a carbide layer composed of TiC0,66, of average thickness equal to 1.5 μm and hardness of 809 ± 79 HV. The treatment of plasma nitriding reduced the values of average roughness of 1.29 μm of the as received condition to 1.18 μm and the plasma carburizing increased this value of 1.28 μm of the sample heat-treated to 2.02 μm. The tests showed that the plasma nitriding reduced the rate of creep and increased the creep life at 600 °C. Based on the values of activation energy in the range 272-309 kJ / mol and the values of stress exponent from 4.82 to 7.28, it was estimated that the dominant mechanism of creep deformation is associated with the climb of dislocations for all experimental conditions. The fractographic analysis revealed that the fracture mechanisms are mainly associated with the nucleation and coalescence of microvoids and decoehasion intergranular.

Estudo do fenômeno da fluência na liga Ti-6AI-4V submetida a tratamentos de nitretação e carbonetação por plasma