The Influence of Post-Quenching Deep Cryogenic Treatment on Tempering Processes and Properties of D2 Tool Steel. Studies of Structure, XRD, Dilatometry, Hardness and Fracture Toughness
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Media type:
E-Article
Title:
The Influence of Post-Quenching Deep Cryogenic Treatment on Tempering Processes and Properties of D2 Tool Steel. Studies of Structure, XRD, Dilatometry, Hardness and Fracture Toughness
Contributor:
Wierszyłłowski, Ignacy
Published:
Trans Tech Publications, Ltd., 2006
Published in:
Defect and Diffusion Forum, 258-260 (2006), Seite 415-420
Language:
Not determined
DOI:
10.4028/www.scientific.net/ddf.258-260.415
ISSN:
1662-9507
Origination:
Footnote:
Description:
A significant increase in durability of cryogenically treated tools after quenching wasreported by a number of publications [1, 2]. As research studies show [4, 5, 6, 7], the main reasonfor this is the kind of carbides precipitated during tempering at temperature range of 150 –200 0C,which is different than in the case of conventional treatment. These carbides are finer and moreevenly distributed in the matrix of steel. The number of carbides is higher than in conventionallytreated steels because of higher fraction of martensite in cryogenically treated steels produced byretained austenite transformation at cooling to deep cryogenic temperatures. The number ofcarbides precipitated from martensite at low temperatures of tempering is proportional to shrinkageproduced at the same temperatures of tempering. Calculations on the basis of dilatometricexperiments show that the shrinkage difference between the same D2 steel cryogenically andconventionally treated is higher than that which results from the increased fraction of martensite incryogenically treated steel. The XRD studies of cryogenically treated steel show a presence of twokinds of martensites differing in tetragonality. Low temperature tempering of cryogenically treatedsteel produced two types of carbides – ε carbide and η carbide. The conventionally treated steelconsists of one kind of tetragonal martensite and one kind of carbide - the ε carbide. The hardnessof cryogenically treated samples was somewhat higher than in conventionally treated ones, whilefracture toughness of conventionally treated samples was somewhat higher than in cryogenicallytreated ones. The results obtained were discussed in reference to literature data.