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Tailoring the Hardening Behavior of 18CrNiMo7‐6 via Cu Alloying
Author(s) -
Bambach Margarita D.,
Bleck Wolfgang,
Kramer Hendrik S.,
Klein Marcus,
Eifler Dietmar,
Beck Tilmann,
Surm Holger,
Zoch HansWerner,
Hoffmann Franz,
Radulescu Aurel
Publication year - 2016
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 - 10.1002/srin.201500129
Subject(s) - materials science , hardening (computing) , metallurgy , martensite , softening , precipitation hardening , strain hardening exponent , composite material , microstructure , layer (electronics)
In order to improve the rolling contact fatigue (RCF) behavior of gear steels, a concept to increase their damage tolerance is developed alternatively to the conventional approach of improving the degree of steel cleanliness. For that purpose, Cu is used as a main alloying element in order to trigger the precipitation of nano‐sized Cu precipitates which shall improve the strain‐hardening rate of the martensitic matrix of Cu‐alloyed 18CrNiMo7‐6 steel surrounding a non‐metallic inclusion during plastic deformation. In this way, early component failure may be avoided and the maintenance costs of, e.g., wind energy converters may be kept low. The experimental analysis shows that nano‐sized Cu precipitates influence the material's strength, ductility, and strain‐hardening behavior under tension, depending on their coherence. Among others, the latter is related to strain‐induced martensitic transformation of coherent Cu. The structure of the Cu precipitates is studied by TEM and SANS analysis. The Cu‐alloyed steel also shows an increased hardening‐exponent CHT studied by cyclic hardness test (CHT) PHYBAL CHT . Fatigue tests of specimens with coherent precipitates show cyclic hardening until a critical stress amplitude. Above that, stress amplitude cyclic softening is detected. An increased damage tolerance could be obtained for a 1 mass‐% Cu‐alloyed 18CrNiMo7‐6 steel.