Crio-têmpera do aço
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INSTITUTO FEDERAL DE EDUCAÇÃO CIÊNCIA E TECNOLOGIACampus Sapucaia do Sul Curso de Engenharia Mecânica
Alessandro Pereira Bederode Juliano Hubner Rodrigues Marco Alves Andretta Rafael Saraiva Cardoso Turma 2E
Disciplina de Ciência dos Materiais Prof. Pedro Carlos Hernandez Júnior
Sapucaia do Sul, 06 de Setembro de 2012
Cryogenic Quenching of Steel Crio-Têmpera do Aço
Abstract Subject to a continuing debate, cryogenic treatments of alloy steels have been claimed to significantly increase wear resistance and toughness through the interplay of three effects: completing martensitic transformation, promoting uniform precipitation of fine carbides and imparting residual stresses. This study reexamines effects of various heattreatment schedules including liquid nitrogen (196°C) and liquid helium (-269°C) quenching on microstructure and selected properties of A2-grade tool steel. Examination methods include SEM, EDS, microhardness, Charpy impact and wear resistance measured using the standard pin-on-disk as well as a diamond stylus micro-scratching technique adopted from the field of thin-film technologies. Results confirm the cryo-treatment enhanced precipitation in the subsequent tempering step of what turns out to be 100-250 nm alloy-depleted carbides, and moderate improvements in wear resistance and hardness, both scaling with the cryogenic treatment time and at the cost of reduced impact resistance. Reported results and correlations provide a basis for optimizing cryo-quench heat-treatment cycle of tool steels and indicate directions for future work.
Resumo Objeto de uma discussão continua, o tratamento criogênico de ligas de aço têm sido usado parta aumentar significantemente a resistência ao desgaste e até mesmo para interação de três efeitos: completar a transformação martensítica, promover uma precipitação uniforme de carbonetos finos e equalização das tensões residuais. Este estudo reexamina os efeitos de vários métodos de tratamento térmico inclusive