Tailoring the Hardening Behavior of 18CrNiMo7‐6 via Cu Alloying. Issue 5 (10th August 2015)

• Record Type: Journal Article
• Authors: Bambach, Margarita D.; Bleck, Wolfgang; Kramer, Hendrik S.; Klein, Marcus; Eifler, Dietmar; Beck, Tilmann; Surm, Holger; Zoch, Hans‐Werner; Hoffmann, Franz; Radulescu, Aurel
• Is Part Of: Steel research international. Volume 87:Issue 5(2016)
• Page Start: 550
• Page End: 561
• Publication Date: 2015-08-10
• Subjects: Cu precipitation -- 18CrNiMo7‐6 -- strain hardening -- cyclic hardness test -- damage tolerance; Steel -- Periodicals; Steel -- Metallurgy -- Periodicals; 669.142
• DOI: 10.1002/srin.201500129
• Languages: English
• ISSNs: 1611-3683

Abstract

Abstract : 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‐exponentCHT studied by cyclic hardness test (CHT) PHYBALCHT . 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. Abstract : To improve the fatigue behavior of gear steels, a concept to increase their damage tolerance is developed. Cu is used in order to trigger 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. Fatigue tests reveal an increased damage tolerance for Cu‐alloyed 18CrNiMo7‐6 steel.