TY - JOUR

T1 - Continuous Cooling Transformation Diagrams of 2.25Cr-1Mo-0.25V Submerged-Arc Weld Metal and Base Metal

AU - Schönmaier, Hannah

AU - Loder, Bernd

AU - Fischer, Thomas

AU - Grimm, Fred

AU - Krein, Ronny

AU - Schmitz-Niederau, Martin

AU - Schnitzer, Ronald

PY - 2020/8

Y1 - 2020/8

N2 - The transformation behavior and microstructural evolution during continuous cooling within the heat affected zone between the weld beads of a 2.25Cr-1Mo-0.25V all-weld metal and the corresponding 2.25Cr-1Mo-0.25V base metal were investigated by means of dilatometer measurements, optical and scanning electron microscopy. Furthermore, macro-hardness measurements were conducted and the ferrite phase fraction was analyzed from optical microscopic images using an imaging processing program. Thereupon a continuous cooling transformation (CCT) diagram for the 2.25Cr-1Mo-0.25V base metal and three welding CCT diagrams with different peak temperatures were constructed to realistically simulate the temperature profile of the different regions within the heat affected zones between the weld beads of the multi-layer weld metal. The microstructural constituents which were observed depending on the peak temperature and cooling parameters are low quantities of martensite, high quantities of bainite and in particular lower bainite, coalesced bainite and upper bainite as well as ferrite for the welding CCT diagrams. Regarding the base metal CCT diagram, all dilatometer specimens exhibited a fully bainitic microstructure consisting of lower bainite, coalesced bainite and upper bainite. Only the slowest cooling rate with a cooling parameter of 50 s caused a ferritic transformation. Nevertheless, it has to be emphasized that the distinction between martensite and bainite and the various kinds of bainite was only possible at higher magnification using scanning electron microscopy.

AB - The transformation behavior and microstructural evolution during continuous cooling within the heat affected zone between the weld beads of a 2.25Cr-1Mo-0.25V all-weld metal and the corresponding 2.25Cr-1Mo-0.25V base metal were investigated by means of dilatometer measurements, optical and scanning electron microscopy. Furthermore, macro-hardness measurements were conducted and the ferrite phase fraction was analyzed from optical microscopic images using an imaging processing program. Thereupon a continuous cooling transformation (CCT) diagram for the 2.25Cr-1Mo-0.25V base metal and three welding CCT diagrams with different peak temperatures were constructed to realistically simulate the temperature profile of the different regions within the heat affected zones between the weld beads of the multi-layer weld metal. The microstructural constituents which were observed depending on the peak temperature and cooling parameters are low quantities of martensite, high quantities of bainite and in particular lower bainite, coalesced bainite and upper bainite as well as ferrite for the welding CCT diagrams. Regarding the base metal CCT diagram, all dilatometer specimens exhibited a fully bainitic microstructure consisting of lower bainite, coalesced bainite and upper bainite. Only the slowest cooling rate with a cooling parameter of 50 s caused a ferritic transformation. Nevertheless, it has to be emphasized that the distinction between martensite and bainite and the various kinds of bainite was only possible at higher magnification using scanning electron microscopy.

KW - 2

KW - 25Cr-1Mo-0

KW - 25V base metal

KW - 25V weld metal

KW - CCT diagram

KW - dilatometer measurement

KW - ferrite phase fraction

KW - hardness

KW - 2.25Cr-1Mo-0.25V base metal

KW - Ferrite phase fraction

KW - Hardness

KW - 2.25Cr-1Mo-0.25V weld metal

KW - Dilatometer measurement

UR - http://www.scopus.com/inward/record.url?scp=85089495579&partnerID=8YFLogxK

U2 - 10.3390/met10081055

DO - 10.3390/met10081055

M3 - Article

VL - 10

SP - 1

EP - 19

JO - Metals : open access journal

JF - Metals : open access journal

SN - 2075-4701

IS - 8

M1 - 1055

ER -