high temperature oxidation behavior of 3d printed, hip and … · 2018-12-07 · high temperature...

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High Temperature Oxidation Behavior of 3D Printed, HIP and Wrought AFA25 Specimen Alloys S. Rashidi 1 , R.K. Gupta 1 , J. Budge 2 , A. Pandey 2 1 Corrosion Engineering, The University of Akron, Akron, OH-44325-3906, USA 2 LG Fuel Cell Systems Inc . North Canton, USA Objective Investigating the influence of manufacturing technologies like wrought, Hot Isostatic pressing (HIP) and Additive manufacturing (AM) on the microstructure and high temperature oxidation behavior of Alumina Forming austenitic (AFA25) alloy. Background Experimental Procedure A new family of alumina forming austenitic stainless steels is under development at Oak Ridge National Laboratory during the past 30 years. AFA 25 stainless steel alloy is known for its excellent corrosion and creep resistance properties at high temperatures [1]. The excellent high temperature corrosion property of AFA25 is due to the formation of an adhesive protective aluminum oxide (Al 2 O 3 ) scale layer on the alloy’s surface [2]. Al 2 O 3 layer provides better oxidation resistance for longer service life at the higher temperature as compared to the chromium oxide layer (Cr 2 O 3 ), which forms on Ni and Fe base alloys [2]. Challenges of AFA stainless steel Alloys Al addition is a major complication for strengthening - Strong BCC stabilizer/delta-ferrite formation (weak) Want to use as little Al as possible to gain oxidation benefit - Keep austenitic matrix for high temperature strength - Introduce second phase for precipitate strengthening Options for Al 2 O 3 Forming Alloys FeCrAl alloys: Open body-centered cubic structure is weak - Not suitable for most structural uses above 500 ° C Ni-Base alloys/Superalloys: too costly - 5 to 10 times greater cost than stainless steels Typically use Al 2 O 3 forming coatings or surface treatment - Not feasible for many applications References 1. M. P. Brady et al., “The development of alumina-forming austenitic stainless steels for high- temperature structural use ,” JOM, vol. 60, no. 7, pp. 1218, Jul. 2008. 2. M. P. Brady, Y. Yamamoto, M. L. Santella, H. Bei, and P. J. Maziasz , “Development of Alumina-Forming Austenitic (AFA) Stainless Steels ,” 23rd Annual Conference on Fossil Energy Materials”, Pittsburg, 2009. 3. L. Yang et al., Additive manufacturing of metals : the technology, materials, design and production”, Springer, Switzerland, 2017. Acknowledgements Work Supported by DE-FE0026098. Future Works Conclusions Results and Discussion Grinding Alloy up to 600 SiC Ultrasonic Cleaning in Acetone (5 min) Store in desiccator for > 1 day Weight the sample for 3 times Temperature: 850 °C Environment: Air Time: 100, 200, 300, 400, 500 & 600 h Pt sputter coating Cu electroplating ( 50 μm thick layer) Cold mounting for cross sectional analysis Grinding up to 1200 SiC Polishing up to 1 μm Characterization: Cross section observation: SEM/EDAX 0 200 400 600 800 1000 0 200 400 600 800 1000 Temp (°C) Hours Oxidation Cycle 100 h 100 h 100 h 100 h 100 h 100 h Cross sectional analysis Sample Preparation High Temperature Test 2. Oxidation Test A. Mass measurement B. Oxidation kinetics 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0 100 200 300 400 500 600 700 ∆m/A (mg/cm 2 ) Time (h) AM16 - AFA 25 AM 1- AFA25 Wrought AFA25 HIP AFA25 AM 1 Wrought AM 16 HIP 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0 200 400 600 800 1000 1200 1400 1600 ∆m/A (mg/cm 2 ) √t √(s) Wrought AFA 25 HIP AFA25 AM 1-AFA25 AM16- AFA25 Alloys Kp (mg/cm 2 s 1/2 ) Wrought AFA 3.00E-05 HIP AFA 6.00E-05 AM1- AFA 6.00E-05 AM16-AFA 3.00E-05 20 μm 10 μm 20 μm 10 μm 50 μm 10 μm 10 μm 50 μm C. As received AM AFA 25 (1) D. As received AM AFA 25 (16) 1. SEM Characterization Before Oxidation A. As received wrought AFA 25 B. As received HIP AFA 25 C. Cross sectional images of AM AFA (1) D. Cross sectional images of AM AFA (16) 20 μm 20 μm 5 μm 2 μm 2 μm 2 μm 2 μm 2 μm 2 μm O Al Nb Cr Fe Ni 20 μm Nb Fe Ni Cr 5 μm 5 μm 5 μm 5 μm 5 μm 5 μm 50 μm 10 μm 3. SEM Characterization After Oxidation 20 μm 20 μm 20 μm 20 μm 20 μm 20 μm 50 μm 20 μm A. Cross sectional images of Wrought AFA25 B. Cross sectional images of HIP AFA25 Al 2 O 3 O Al Nb Fe Ni Cr Bright particles: Nb and Mo rich (EDX) Darker phases: pores or Al rich Higher fraction of Nb rich particles in HIP alloy 16 AM-AFA alloys were prepared with Selective Laser Melting (SLM) technique using a wide range of AM parameters: Laser intensity, Hatch, focus and speed were varied. AM alloys had uniform microstructure which was attributed to the fast cooling rates involved in the AM process The microstructure of fine precipitates depends upon the AM processing parameters. Mass gain per unit area for wrought and HIP AFA 25 along with that of AM AFA 25. The mass gain of AM alloys is represented by the region shaded in blue. The AM AFA 25 alloys showed good oxidation resistance which was comparable with that of the wrought and HIP AM alloys. The high temperature oxidation resistance of AM alloys was dependent upon the AM parameters. Formation of an external alumina scale. precipitation of bright Mo-Nb rich phases during oxidation. Well adherent, protective, external alumina layer formed on AFA25 alloys at 850 °C. AM AFA25 processed by different parameters showed similar oxidation behavior like wrought and HIP alloys. AM can be used to produce AFA25 alloy without compromising the high temperature oxidation behavior. Selective Laser Melting Results and Discussion Oxide Scale Cu plating Future work will focus on the in-depth characterization by using TEM, FIB. The oxidation test will run for longer time (1000 hrs) 50 μm 20 μm 5 μm 5 μm 5 μm 5 μm 5 μm 5 μm 5 μm 5 μm Al O Nb Cr Fe Ni Mn O Cr Ni Nb Al Fe 20 μm 20 μm 20 μm 20 μm 20 μm 20 μm Mn 20 μm

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Page 1: High Temperature Oxidation Behavior of 3D Printed, HIP and … · 2018-12-07 · High Temperature Oxidation Behavior of 3D Printed, HIP and Wrought AFA25 Specimen Alloys 1S. Rashidi

High Temperature Oxidation Behavior of 3D Printed, HIP and Wrought AFA25 Specimen Alloys S. Rashidi1, R.K. Gupta1, J. Budge2, A. Pandey2

1Corrosion Engineering, The University of Akron, Akron, OH-44325-3906, USA 2 LG Fuel Cell Systems Inc. North Canton, USA

Objective

Investigating the influence of manufacturing technologies like wrought, Hot Isostatic pressing

(HIP) and Additive manufacturing (AM) on the microstructure and high temperature oxidation

behavior of Alumina Forming austenitic (AFA25) alloy.

Background

Experimental Procedure

A new family of alumina forming austenitic stainless steels is under development at Oak

Ridge National Laboratory during the past 30 years.

AFA 25 stainless steel alloy is known for its excellent corrosion and creep resistance properties

at high temperatures [1].

The excellent high temperature corrosion property of AFA25 is due to the formation of an

adhesive protective aluminum oxide (Al2O3) scale layer on the alloy’s surface [2].

Al2O3 layer provides better oxidation resistance for longer service life at the higher temperature

as compared to the chromium oxide layer (Cr2O3), which forms on Ni and Fe base alloys [2].

Challenges of AFA stainless steel Alloys

• Al addition is a major complication for

strengthening

- Strong BCC stabilizer/delta-ferrite

formation (weak)

• Want to use as little Al as possible to gain

oxidation benefit

- Keep austenitic matrix for high temperature

strength

- Introduce second phase for precipitate

strengthening

Options for Al2O3 Forming Alloys

• FeCrAl alloys: Open body-centered

cubic structure is weak

- Not suitable for most structural uses

above 500 °C

• Ni-Base alloys/Superalloys: too costly

- 5 to 10 times greater cost than

stainless steels

• Typically use Al2O3 forming coatings or

surface treatment

- Not feasible for many applications

20 m

References

• 1. M. P. Brady et al., “The development of alumina-forming austenitic stainless steels for high-

temperature structural use,” JOM, vol. 60, no. 7, pp. 12–18, Jul. 2008.

• 2. M. P. Brady, Y. Yamamoto, M. L. Santella, H. Bei, and P. J. Maziasz, “Development of

Alumina-Forming Austenitic (AFA) Stainless Steels,” 23rd Annual Conference on Fossil Energy

Materials”, Pittsburg, 2009.

• 3. L. Yang et al., “Additive manufacturing of metals : the technology, materials, design and

production”, Springer, Switzerland, 2017.

Acknowledgements

• Work Supported by DE-FE0026098.

Future Works

Conclusions

Results and Discussion

100 µm

20 µm

• Grinding Alloy up to 600 SiC

Ultrasonic Cleaning in Acetone (5 min)

Store in desiccator for > 1 day

Weight the sample for 3 times

Temperature: 850 °C

Environment: Air

Time: 100, 200, 300, 400, 500 & 600 h

Pt sputter coating

Cu electroplating (≈ 50 µm thick layer)

Cold mounting for cross sectional

analysis

Grinding up to 1200 SiC

Polishing up to 1 µm

Characterization:

Cross section observation: SEM/EDAX

0

200

400

600

800

1000

0 200 400 600 800 1000

Tem

p (°

C)

Hours

Oxidation Cycle

100 h 100 h 100 h 100 h 100 h 100 h

Cross sectional analysis

Sample Preparation

High Temperature Test

2. Oxidation Test

A. Mass measurement B. Oxidation kinetics

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 100 200 300 400 500 600 700

∆m

/A (

mg

/cm

2)

Time (h)

AM16 - AFA 25AM 1- AFA25Wrought AFA25HIP AFA25

AM 1

Wrought

AM 16

HIP

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 200 400 600 800 1000 1200 1400 1600

∆m

/A (

mg

/cm

2)

√t √(s)

Wrought AFA 25

HIP AFA25

AM 1-AFA25

AM16- AFA25

Alloys Kp (mg/cm2s1/2)

Wrought AFA 3.00E-05

HIP AFA 6.00E-05

AM1- AFA 6.00E-05

AM16-AFA 3.00E-05

20 µm 10 µm 20 µm 10 µm

50 µm 10 µm 10 µm 50 µm

C. As received AM AFA 25 (1) D. As received AM AFA 25 (16)

1. SEM Characterization Before Oxidation

A. As received wrought AFA 25 B. As received HIP AFA 25

C. Cross sectional images of AM AFA (1) D. Cross sectional images of AM AFA (16)

20 µm

20 µm 5 µm

2 µm 2 µm 2 µm

2 µm 2 µm 2 µm

O Al Nb

Cr Fe Ni

20 µm

Nb Fe

Ni Cr

5 µm

5 µm

5 µm

5 µm

5 µm

5 µm

50 µm 10 µm

3. SEM Characterization After Oxidation

20 µm 20 µm

20 µm 20 µm

20 µm 20 µm

50 µm 20 µm

A. Cross sectional images of Wrought AFA25 B. Cross sectional images of HIP AFA25

Al2O3

O Al

Nb Fe

Ni Cr

• Bright particles: Nb and Mo rich (EDX)

• Darker phases: pores or Al rich • Higher fraction of Nb rich particles

in HIP alloy

• 16 AM-AFA alloys were prepared with

Selective Laser Melting (SLM) technique

using a wide range of AM parameters:

Laser intensity, Hatch, focus and speed

were varied.

• AM alloys had uniform microstructure which was attributed to the fast cooling rates involved

in the AM process

• The microstructure of fine precipitates depends upon the AM processing parameters.

• Mass gain per unit area for wrought and

HIP AFA 25 along with that of AM AFA

25. The mass gain of AM alloys is

represented by the region shaded in blue.

• The AM AFA 25 alloys showed good oxidation resistance which was comparable with that

of the wrought and HIP AM alloys.

• The high temperature oxidation resistance of AM alloys was dependent upon the AM

parameters.

• Formation of an external alumina scale.

• precipitation of bright Mo-Nb rich phases

during oxidation.

• Well adherent, protective, external alumina layer formed on AFA25 alloys at 850 °C.

• AM AFA25 processed by different parameters showed similar oxidation behavior like

wrought and HIP alloys.

• AM can be used to produce AFA25 alloy without compromising the high temperature

oxidation behavior.

Selective Laser Melting

Results and Discussion

Oxide Scale Cu plating

• Future work will focus on the in-depth characterization by using TEM, FIB.

• The oxidation test will run for longer time (1000 hrs)

50 µm 20 µm

5 µm

5 µm

5 µm

5 µm

5 µm

5 µm

5 µm 5 µm

Al

O

Nb

Cr Fe

Ni Mn

O

Cr Ni

Nb

Al

Fe

20 µm 20 µm

20 µm 20 µm

20 µm 20 µm

Mn

20 µm