Microstructural Characterization of Ledeburitic Tool Steel after Sub-Zero Treatment and Tempering

Abstract:

Microstructural characterization of ledeburitic tool steel Vanadis 6 after sub-zero treatment and tempering has been examined. The samples were heat treated using following schedules: heating to the austenitizing temperature (T_A = 1050 °C) in a vacuum furnace, hold at the final temperature for 30 min. and nitrogen gas quenching (5 bar). The sub-zero treatments consisted of immediate (after quenching) immersion of the material into the liquid helium (-269 °C), hold at the soaking temperature and removal the samples to be heated to a room temperature. Double tempering has been performed at the temperatures from the range 170 – 530 °C, whereas each tempering cycle was realized with a hold of 2 h. Typical heat treated microstructure of ledeburitic steels consists, besides of the martensitic matrix with certain amount of retained austenite, of several types of carbides – eutectic, secondary and small globular carbides. In sub-zero treated steel the amount of retained austenite is significantly reduced. The population density of small globular carbides increase as a result of sub-zero treating. Tempering of the material resulted in decrease in population density of small globular carbides with increasing the tempering temperature. The hardness of sub-zero treated material is higher than that of conventionally quenched one. Also, this tendency is preserved when the steel is low-temperature tempered. On the other hand, the hardness of conventionally quenched steel becomes higher than that of SZT one when tempered at the temperature of secondary hardening.

• Periodical: Defect and Diffusion Forum (Volume 403)
• Pages: 103-109
• DOI: https://doi.org/10.4028/www.scientific.net/DDF.403.103
• Online since: September 2020
• Authors: Jana Ptačinová*, Juraj Ďurica, Matej Pašák, Martin Kusý, Peter Jurči
• Keywords: Carbides, Ledeburitic Steel, Martensite, Sub-Zero Treatment

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