V. Neubert, R. Doelling, E. Schulze
Dr R Doelling and Prof Dr V Neubert
Institute for Materials Testing and Materials Engineering
Clausthal-Zellerfeld, Germany
Mrs. Elisabeth Schulze, Research Student, Technische Hochschule Halle/Merseburg, Germany
Abstract
Results of a European concerted research project on the improvement of Super Duplex Cast Alloys are presented.
The influence of the ferrite grain size and the type and size of slag inclusions of SDCAs on the corrosion resistance and mechanical properties was evaluated.
Materials investigated:
SDCAs in the range of: Cr 25 - 27%; Mo 3 - 5%, Ni 6 - 8%
Properties investigated:
0.2 Yield, UTS, Impact, CTOD
Pitting, crevice corrosion, SSCC constant load and SSRT-method 2.56 x 10-7 1/s
Metallurgical investigations:
Grain size, size and type of slag inclusions (oxides, sulphides)
Results
Decrease in the ferrite grain size leads to:
- significant increase of Impact and Yield strength
- marginal increase of CPT and CCT
- significant increase of SSCC
Influence of slag inclusions:
Presence of REM sulphides and/or oxisulphides decrease CPT and CCT values and SSCC resistance which can be achieved and should therefore be avoided.
The size of oxides and (Fe,Mn)- sulphides has a direct and strong influence especially on the SSCC resistance.