Made available in DSpace on 2014-12-17T14:06:50Z (GMT). No. of bitstreams: 1 MariaLMM.pdf: 1059040 bytes, checksum: e385dd512eb484e085eb027acc2a89fe (MD5) Previous issue date: 2008-08-22 / In this research there was an evaluation of the best conditions of nitriding in plasma within a cathodic cage at an atmosphere of 80% N2-20%H2 in samples of tool manganese steel AISI D6, cold working, treated thermally in the following conditions: tension relief, treated thermally to temperature of maximum heat, temperate heat and temperate and temperate heat. A pressure of 2.5mbar and temperatures of 400 and 300?C com treatment time of two and three hours were used to evaluate its performance as cutting tool (punch) of bicycle backs. Hardness, micro-structural aspects (layer thickness, interface, grain size etc), and crystal phases on the surface were appraised. When treated to tension relief, thermally treated to maximum heat temperature, temperature and temperate heat, the samples presented hardness levels of 243HV, 231HV, 832HV, and 653HV, respectively. The best nitrification conditions were: four hours and 300?C for heat samples. A superficial hardness of 1000HV and a 108?m thickness for the nitrided layer were found in these samples / Neste trabalho, foi realizada a avalia??o das melhores condi??es de nitreta??o em plasma com gaiola cat?dica, em atmosfera de 80%N2 - 20%H2 em amostras de a?o ferramenta para trabalho a frio AISI D6, tratado termicamente nas condi??es: al?vio de tens?o, tratado termicamente na temperatura de revenimento m?ximo, temperada e temperada e revenida. Usou-se press?o de 2,5 mbar, temperaturas de 400 e 300?C com tempo de tratamento de 3 e 4 horas, visando avaliar o seu desempenho em ferramenta de corte (pun??o) de rabeiras de bicicletas. Estimou-se a dureza, aspectos microestruturais (espessura da camada, interface, tamanho de gr?o, etc.) e fases cristalinas presentes na superf?cie. As amostras apresentaram n?veis de durezas 243HV, 231HV, 832HV e 653HV para as amostras com al?vio de tens?o, tratada termicamente na temperatura de revenimento m?ximo, temperada e temperada e revenida, respectivamente. As melhores condi??es de nitreta??o foram 4 horas a 300?C para as amostras temperadas e revenidas. As mesmas apresentaram uma dureza superficial em torno de 1000HV e 100?m de espessura para a camada nitretada