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Changes in Tempering and its Effect on Precipitation Behaviour in a Hot‐work Tool Steel
Author(s) -
Mayer Svea,
Leitner Harald,
Scheu Christina,
Siller Ingo,
Clemens Helmut
Publication year - 2009
Publication title -
steel research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.603
H-Index - 49
eISSN - 1869-344X
pISSN - 1611-3683
DOI - 10.2374/sri08sp116_89
Subject(s) - bainite , martensite , tempering , continuous cooling transformation , lath , materials science , metallurgy , microstructure , carbide , austenite , cementite , transmission electron microscopy , nanotechnology
The microstructural characteristics of the hot‐worked and subsequently tempered tool steel grade X38CrMoV5‐1 was studied as a function of the cooling rate using transmission electron microscopy and three‐dimensional atom probe. According to the continuous cooling transformation diagram different cooling rates were chosen to adjust a fully martensitic or mixed microstructure consisting of martensite and bainite. The sample with the highest cooling rate exhibited a martensitic structure with nanometre sized secondary hardening carbides of the type M 3 C, M 2 C, M 7 C 3 , and MC. M 3 C and M 2 C were not stable and transformed to M 7 C 3 as the cooling rate decreased. Furthermore, with decreasing cooling rates an increasing number of M 7 C 3 precipitates are particularly present at former austenite grain boundaries as well as martensite and bainite lath boundaries, which strongly affects the mechanical properties.