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

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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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