Post on 28-Nov-2014
description
Heat resistant austenitic stainless steels
Master research project
Student : Andrey GRISHIN
Tutor: Anna FRACZKIEWICZ Karolina MAMINSKA
Andrey GRISHIN - Master Research Student
Natural Gas Reforming
Gasification
Photobiological and
Photoelectroche-mical
Renewable Liquid
Reforming
Nuclear High-Temperature Electrolysis
Andrey GRISHIN - Master Research Student
Production of hydrogen
2
≈ 90 %
• 800-1100 °C• 1-4 MPа• Length 10-12 m
• Interneal• diametetre• 80-115mm• Thickness• 10-20mm
• CH4 + H2O → →CO + 3H2 + +191,7 kJ/mol
3
Natural Gas Reforming
Andrey GRISHIN - Master Research Student
http://www.hydrocarbonprocessing.com/Article/2598005.html
Andrey GRISHIN - Master Research Student
Stages of creep Creep damage
Modes of creep:
Creep of reformer tubes
Creep
Laser-Optic TubeInspection Method
4http://www.ndt.net/article/v10n03/roberts/roberts.htm
T>0,5 Tm
σ=const
Dislocation creep
Diffusion creep
Dislocation creep
Andrey GRISHIN - Master Research Student 5
http://engineering.dartmouth.edu/defmech/chapter_2.htm
Power-law breakdown: glide contributes increasingly to the overall strain-rate
kT
bD2
3
Diffusional flow by diffusional transport through and round the grains. The strain-rate may be limited by the rate of diffusion or by that of an interface reaction.
Diffusion creep
Andrey GRISHIN - Master Research Student 6
http://engineering.dartmouth.edu/defmech/chapter_2.htm
kTd
DNH 2
kTd
D jCo 3
Heat resistant alloys of HP type
Andrey GRISHIN - Master Research Student 7
Ni 33-37Cr 24-28C 0.35-
0.75Fe - bal
Nb ~ 0,6-0,8 Ti ~ 0,05V ~ 0,05
Si ~ 1Al ~ 0,01 Mo ~ 0,05Mn ~ 0,8W ~ 0,05
HP alloyChem.comp.
%
Corrosion resistance
Austenitestabilization
Precipitation of fine carbidesintragranulary
Precipitationof carbides andsolid solutionStrengthening effect
Andrey GRISHIN - Master Research Student
Centrifugal casting technique
8http://www.centrifugalcasting.com/technical.htm
Any length, thickness
and diameter
Resistant to atmosphe-ric corrosion
The rotation
speed from
250 to 3600
RPM
Cooling-down is very fast
Andrey GRISHIN - Master Research Student
Solidification
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1- Liquid2-Austenite3- NbC4- Cr7C3
5- Cr23C6
Big size of grains (mm)
Dendritic structure
Primary carbides (NbC, Cr7C3,
Cr23C6)
Andrey GRISHIN - Master Research Student
As-cast material
10
Microstructure evolution of HP40-Nb alloys during aging underair at 1000 °CRaluca Voicua, Eric Andrieua, Dominique Poquillona, Jader Furtadob, Jacques Lacazea,⁎
Andrey GRISHIN - Master Research Student
In-service state
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600 700 800 900 1000 1100 1200 1300 1400 15000
10
20
30
40
50
60
70
80
90
100
Liquid
Austenite
NbC
M7C3
M23C6
T, °C
C (Phase) wt %
1200 1220 1240 1260 1280 1300 13200
1
2
3
4
5
6
Andrey GRISHIN - Master Research Student
In-service state
12
Aging:850°C, 48h
Andrey GRISHIN - Master Research Student
In-service state
13
1
2
3
EDX analysis
Andrey GRISHIN - Master Research Student
Conclusion
14
The microstructure of the as-cast alloy is austenitic with the primary Cr- and Nb-carbides
In the in-service state the microstructure of alloy is changed: the secondary precipitation occurs in the matrix
In order to impose the mechanical propertiessuch as creep resistance we need to obtain the fine secondary precipitates dispersed in the matrix
Andrey GRISHIN - Master Research Student
What next?
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•Qualitative and quantitative analysis.
•Technics: SEM, TEM, EDX...
The study of microstructure
transformation of one of the HP alloy modifications. Qualitative and
quantitative analysis using
Andrey GRISHIN - Master Research Student
Thank you for your attention!
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