Nitrided Steel
Nitrided Steel Group Members
Kurtis Carlock David Griggs Christina Lehman Phillip Levins R.J. Santucci
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Introduction and Background Gas Nitriding
•Method of hardening steels without deformation or phase change
•Low-carbon, low-alloy steels baked at low temperature (~1100°F) in a nitrogen-rich atmosphere
•Nitrogen diffuses into the surface, providing case-hardening and corrosion resistance
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Introduction and Background Ferritic Nitro-Carburizing (FNC)
•Similar to Gas Nitriding
•Steel baked at even lower temperature (~1000°F) in atmosphere containing Nitrogen and Carbon
•Both N and C diffuse interstitially into the ferrite structure •Outer surface of the steel hardened and protected
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Introduction and Background Questions Considered: •What occurs during Nitriding? • Hardening? • Changes in the composition? • Effects on the microstructure?
•What type of steel is this? • Look at the composition
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Samples 1. 2. 3.
Gas nitrided steel @ 1100°F for 24 hours Ferritic Nitro-carburized (FNC) steel @ 1000°F for 5 hours Base steel (untreated)
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Sample Preparation •Sectioning: • Cut with a diamond saw
•Mounting: • Hot mounted with epoxy
Cross-Section
•Polishing: • Polished up to 1 micron finish •Etching: • 1-3% Nital etchant Bulk
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Characterization Techniques Overview Vickers Test: Found/compared the hardness values of each sample • •
Bulk applied load: 0.5 kg Cross-Section applied load: 0.1 kg
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Characterization Techniques Overview • Optical: Looked at the general microstructure of each sample • Hirox KH 7700
http://www.medicaldevicenow.com/contents/displayImage/2914
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Characterization Techniques Overview •SEM and EDS: Mainly used to find composition of each of the cross-sections • JEOL 6700F Scanning Electron Microscope
http://www.virginia.edu/ms/nmcf/imgs/sidebar_joel6.jpg
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Base Steel Grain boundaries
Bulk Spring Presentations 2012
Materials Science Investigations, MSE 3101
Base Steel Top cross-section
mount
Bottom cross-section
Cross-Section Spring Presentations 2012
Materials Science Investigations, MSE 3101
FNC Steel
Bulk
Spring Presentations 2012
Materials Science Investigations, MSE 3101
FNC Steel Top cross-section
Nitrided layer
mount
Bottom cross-section
Cross-Section Spring Presentations 2012
Materials Science Investigations, MSE 3101
Nitrided Steel
Bulk Spring Presentations 2012
Materials Science Investigations, MSE 3101
Nitrided Steel Top cross-section Oxides
mount
Nitrided layer
Bottom cross-section
Cross-Section Spring Presentations 2012
Materials Science Investigations, MSE 3101
Grain Size Analysis - Base 17 15 11 16 14 16 13 11 16 17
200 µm Spring Presentations 2012
Materials Science Investigations, MSE 3101
The average grain size for the base steel is 147µm2
Grain Size Analysis - FNC 14 10 12 16 16 14 13 15 12 10
200 µm Spring Presentations 2012
Materials Science Investigations, MSE 3101
The average grain size for the FNC steel is 180µm2
Grain Size Analysis - Nitrided 16 13 11 12 16 12 10 11 12 11
200 µm Spring Presentations 2012
Materials Science Investigations, MSE 3101
The average grain size for the Nitrided steel is 204µm2
SEM of Base Cross-Section
Spring Presentations 2012
Materials Science Investigations, MSE 3101
SEM of Base Cross-Section
No visible differences at edges of material
Spring Presentations 2012
Materials Science Investigations, MSE 3101
SEM of FNC Cross-Section
Oxides
Spring Presentations 2012
Materials Science Investigations, MSE 3101
SEM of FNC Cross-Section
Visibly nitrided layers
Spring Presentations 2012
Materials Science Investigations, MSE 3101
SEM of Nitrided Cross-Section
Beginning of visibly nitrided layer
Oxides
Spring Presentations 2012
Materials Science Investigations, MSE 3101
SEM of Nitrided Cross-Section
Visibly nitrided layers Dendrites
Oxides
Spring Presentations 2012
Materials Science Investigations, MSE 3101
EDS of Nitrided Cross-Section
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Summary of EDS Results
Spring Presentations 2012
Sample Type
Fe (Wt%)
Mn (Wt%)
Base
98.74
1.26
FNC
98.77
1.23
Nitrided
98.85
1.15
Materials Science Investigations, MSE 3101
Hardness Testing Hardness points decrease in size when closer to nitrided layer
Vickers Screenshot of Nitrided Cross-Section Spring Presentations 2012
Materials Science Investigations, MSE 3101
Hardness Testing mount
212 HV
edge
474 HV 563 HV
260 HV
edge
Shape Change Indicates Change in Hardness
mount
FNC Cross-Section Spring Presentations 2012
176 HV
Nitrided Cross-Section
Materials Science Investigations, MSE 3101
Comparison of Bulk Hardness
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Comparison of Cross-Section Hardness 700
Cross Entire Profile
600
Vicker's Hardness Value
500
400 Base Cross
Nitride Cross
300
FNC Cross 200
100
0
0
2
4
6
8
10
12
14
16
Trial
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Comparison of Cross-Section Hardness Cross Internal 190
Vicker's Hardness Value
170
150 Base Cross Internal Nitride Cross Internal FNC Cross Internal
130
Consistent hardness values 110
90 3
4
5
6
7
8
9
Trial
SEM of Base Cross-Section Spring Presentations 2012
Materials Science Investigations, MSE 3101
Average Hardness Average Hardness Values 400 337.5385
350
Hardness (HV)
300 250 177.9
200 150
111.5
188.8571
194.8 Bulk Cross-Section
102.5833
100 50 0 Base
FNC
Nitrided
Sample Type
Demonstrates overall how the hardness of each sample compares. However, need to analyze each sample individually to see how there is variation within the sample. Spring Presentations 2012
Materials Science Investigations, MSE 3101
Results •FNC and nitrided steels have higher hardness
• Bulk samples: 195.4HV (Nitrided) and 177.9HV (FNC) vs 111.5HV (base steel)
•
Hirox images show visibly nitrided region • Region of clear diffusion (~20-60𝜇𝑚 into the sample)
•
EDS analysis inconclusive for nitrogen • Nitrogen is low atomic mass; may not be detectable by EDS • Main metallic components are Iron (>98%) and Manganese (1-2%)
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Discussion • Nitriding steel was found to increase hardness as compared to base steel
•Errors
• Not able to detect presence of nitrogen in samples using EDS • Vickers hardness near edge of sample is inconclusive
•Quantify nitrogen content in steel
• Potential techniques include Auger Electron Spectroscopy (AES), Time of Flight Secondary Ion Mass Spectroscopy (TOF-SIMS), or Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Summary • The goal was to determine if and to what extent nitriding steel affects its physical properties
•
The hardness of Nitrided and FNC steel was found to be greater than that of a base steel
•
Further experimentation • Quantify the amount of nitrogen in the samples
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Acknowledgements
•Jim Dusin & Kyle Cox, Pantheon Steel LLC •Matt Steiner •Mike Melia •Professor Fitz-Gerald
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Kurtis Carlock David Griggs Christina Lehman Phillip Levins R.J. Santucci
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Introduction and Background Gas Nitriding
•Method of hardening steels without deformation or phase change
•Low-carbon, low-alloy steels baked at low temperature (~1100°F) in a nitrogen-rich atmosphere
•Nitrogen diffuses into the surface, providing case-hardening and corrosion resistance
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Introduction and Background Ferritic Nitro-Carburizing (FNC)
•Similar to Gas Nitriding
•Steel baked at even lower temperature (~1000°F) in atmosphere containing Nitrogen and Carbon
•Both N and C diffuse interstitially into the ferrite structure •Outer surface of the steel hardened and protected
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Introduction and Background Questions Considered: •What occurs during Nitriding? • Hardening? • Changes in the composition? • Effects on the microstructure?
•What type of steel is this? • Look at the composition
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Samples 1. 2. 3.
Gas nitrided steel @ 1100°F for 24 hours Ferritic Nitro-carburized (FNC) steel @ 1000°F for 5 hours Base steel (untreated)
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Sample Preparation •Sectioning: • Cut with a diamond saw
•Mounting: • Hot mounted with epoxy
Cross-Section
•Polishing: • Polished up to 1 micron finish •Etching: • 1-3% Nital etchant Bulk
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Characterization Techniques Overview Vickers Test: Found/compared the hardness values of each sample • •
Bulk applied load: 0.5 kg Cross-Section applied load: 0.1 kg
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Characterization Techniques Overview • Optical: Looked at the general microstructure of each sample • Hirox KH 7700
http://www.medicaldevicenow.com/contents/displayImage/2914
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Characterization Techniques Overview •SEM and EDS: Mainly used to find composition of each of the cross-sections • JEOL 6700F Scanning Electron Microscope
http://www.virginia.edu/ms/nmcf/imgs/sidebar_joel6.jpg
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Base Steel Grain boundaries
Bulk Spring Presentations 2012
Materials Science Investigations, MSE 3101
Base Steel Top cross-section
mount
Bottom cross-section
Cross-Section Spring Presentations 2012
Materials Science Investigations, MSE 3101
FNC Steel
Bulk
Spring Presentations 2012
Materials Science Investigations, MSE 3101
FNC Steel Top cross-section
Nitrided layer
mount
Bottom cross-section
Cross-Section Spring Presentations 2012
Materials Science Investigations, MSE 3101
Nitrided Steel
Bulk Spring Presentations 2012
Materials Science Investigations, MSE 3101
Nitrided Steel Top cross-section Oxides
mount
Nitrided layer
Bottom cross-section
Cross-Section Spring Presentations 2012
Materials Science Investigations, MSE 3101
Grain Size Analysis - Base 17 15 11 16 14 16 13 11 16 17
200 µm Spring Presentations 2012
Materials Science Investigations, MSE 3101
The average grain size for the base steel is 147µm2
Grain Size Analysis - FNC 14 10 12 16 16 14 13 15 12 10
200 µm Spring Presentations 2012
Materials Science Investigations, MSE 3101
The average grain size for the FNC steel is 180µm2
Grain Size Analysis - Nitrided 16 13 11 12 16 12 10 11 12 11
200 µm Spring Presentations 2012
Materials Science Investigations, MSE 3101
The average grain size for the Nitrided steel is 204µm2
SEM of Base Cross-Section
Spring Presentations 2012
Materials Science Investigations, MSE 3101
SEM of Base Cross-Section
No visible differences at edges of material
Spring Presentations 2012
Materials Science Investigations, MSE 3101
SEM of FNC Cross-Section
Oxides
Spring Presentations 2012
Materials Science Investigations, MSE 3101
SEM of FNC Cross-Section
Visibly nitrided layers
Spring Presentations 2012
Materials Science Investigations, MSE 3101
SEM of Nitrided Cross-Section
Beginning of visibly nitrided layer
Oxides
Spring Presentations 2012
Materials Science Investigations, MSE 3101
SEM of Nitrided Cross-Section
Visibly nitrided layers Dendrites
Oxides
Spring Presentations 2012
Materials Science Investigations, MSE 3101
EDS of Nitrided Cross-Section
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Summary of EDS Results
Spring Presentations 2012
Sample Type
Fe (Wt%)
Mn (Wt%)
Base
98.74
1.26
FNC
98.77
1.23
Nitrided
98.85
1.15
Materials Science Investigations, MSE 3101
Hardness Testing Hardness points decrease in size when closer to nitrided layer
Vickers Screenshot of Nitrided Cross-Section Spring Presentations 2012
Materials Science Investigations, MSE 3101
Hardness Testing mount
212 HV
edge
474 HV 563 HV
260 HV
edge
Shape Change Indicates Change in Hardness
mount
FNC Cross-Section Spring Presentations 2012
176 HV
Nitrided Cross-Section
Materials Science Investigations, MSE 3101
Comparison of Bulk Hardness
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Comparison of Cross-Section Hardness 700
Cross Entire Profile
600
Vicker's Hardness Value
500
400 Base Cross
Nitride Cross
300
FNC Cross 200
100
0
0
2
4
6
8
10
12
14
16
Trial
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Comparison of Cross-Section Hardness Cross Internal 190
Vicker's Hardness Value
170
150 Base Cross Internal Nitride Cross Internal FNC Cross Internal
130
Consistent hardness values 110
90 3
4
5
6
7
8
9
Trial
SEM of Base Cross-Section Spring Presentations 2012
Materials Science Investigations, MSE 3101
Average Hardness Average Hardness Values 400 337.5385
350
Hardness (HV)
300 250 177.9
200 150
111.5
188.8571
194.8 Bulk Cross-Section
102.5833
100 50 0 Base
FNC
Nitrided
Sample Type
Demonstrates overall how the hardness of each sample compares. However, need to analyze each sample individually to see how there is variation within the sample. Spring Presentations 2012
Materials Science Investigations, MSE 3101
Results •FNC and nitrided steels have higher hardness
• Bulk samples: 195.4HV (Nitrided) and 177.9HV (FNC) vs 111.5HV (base steel)
•
Hirox images show visibly nitrided region • Region of clear diffusion (~20-60𝜇𝑚 into the sample)
•
EDS analysis inconclusive for nitrogen • Nitrogen is low atomic mass; may not be detectable by EDS • Main metallic components are Iron (>98%) and Manganese (1-2%)
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Discussion • Nitriding steel was found to increase hardness as compared to base steel
•Errors
• Not able to detect presence of nitrogen in samples using EDS • Vickers hardness near edge of sample is inconclusive
•Quantify nitrogen content in steel
• Potential techniques include Auger Electron Spectroscopy (AES), Time of Flight Secondary Ion Mass Spectroscopy (TOF-SIMS), or Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Summary • The goal was to determine if and to what extent nitriding steel affects its physical properties
•
The hardness of Nitrided and FNC steel was found to be greater than that of a base steel
•
Further experimentation • Quantify the amount of nitrogen in the samples
Spring Presentations 2012
Materials Science Investigations, MSE 3101
Acknowledgements
•Jim Dusin & Kyle Cox, Pantheon Steel LLC •Matt Steiner •Mike Melia •Professor Fitz-Gerald
Spring Presentations 2012
Materials Science Investigations, MSE 3101
