The objective of the present work is to establish the heat treating parameters necessary to impose to a pair of high chromium white cast irons a hardness figure in the range from 35 to 40 HRC, acceptable to guarantee a reasonable machinability of the material. Samples of two high chromium white cast irons have been isothermally annealed under different conditions. The evolution of the phase transformations during the annealing process has been evaluated by dilatometry, supported by optical and scanning electron microscopy, x-ray microanalysis (EDS) and hardness evaluation. The results from this work demonstrate that the recommended procedure for the soft annealing treatment of the high chromium white cast irons consists of a destabilizing step in the austenitic domain followed by an isothermal decomposition of the austenite in the ferritic domain.

No abstract

No abstract

como parte dos requisitos para a obtenção do título de Mestre em Ciências (Química). Dedicatória Ao Deus da minha vida, Senhor e Salvador Jesus Cristo Aos meus pais Zezé e Amorim À minha amada noiva Marla Bruna Aos meus irmãos Dane e Herbert, meu cunhado Fábio e sobrinhas Isa e DudaA toda minha família, tios e primos, e em especial: Voinha, Almerinda Souza Andrade (in memoniam). AgradecimentosEste trabalho representou para mim não apenas um processo de especialização acadêmica, mas principalmente um processo de vida, em todos os sentidos.A Deus, pois mesmo sem merecer, deu-me a grata oportunidade de cursar o mestrado, deu-me força e coragem para não desistir, deu-me ânimo, cercou-me de amigos, e em todos os momentos esteve comigo, não tenho palavras para ΔS fus = 0,92 J °C -1 g -1 ), followed by decomposition in a single step between 191,8-900,0 °C, in which a dimmer is formed after release of ammonia and the isopropylamines in the edges of the molecules. Then ammonia, isporpyl alcohol, carbonic gas and water were released. Kinetic studies by the isoconvertional method showed activation energy E a = 102 ± 3 kJ mol -1 and exponential pre-factor log A = 9,2 ± 0,3 min -1 for the solid state thermal decomposition reaction. Polymorphism studies for nadolol revealed that at least two enantiomeric forms of the compound can be isolated in, by varying the solvent and the temperature of crystallization.