Bracker, Gwendolyn

Hodges, Elizabeth

Hyers, Robert

Phillips, Brandon

SanSoucie, Michael

Walko, Ethan

English

NASA Technical Reports Server

1Effects of Oxygen Partial Pressure on the 
Surface Tension of Liquid Aerospace Alloys
Michael SanSoucie
Brandon Phillips
NASA Marshall Space Flight Center
Gwendolyn Bracker
Elizabeth Hodges
Ethan Walko
Robert Hyers
University of Massachusetts
https://ntrs.nasa.gov/search.jsp?R=20200001740 2020-03-28T19:09:27+00:00Z
2The Team
Bob Hyers, Gwendolyn Bracker, Elizabeth Hodges, Paul Craven, 
Trudy Allen, and Glenn Fountain
3Motivation for Thermophysical Properties
• Need high quality thermophysical 
properties of high-temperature 
materials.
• These properties are critical for 
developing accurate models with 
predictive capability
– Casting
– Welding
– Additive Manufacturing
• Measurements will improve 
manufacturing of propulsion 
components, leading to higher 
performance and higher reliability.
A model of a casting process.
Reference: 
http://www.technalysis.com/casting_software.a
spx
4Need for Oxygen Partial Pressure Control
• Surface tension of molten metals 
is affected by even a small 
amount of adsorption of oxygen
– Oxidation may have an impact of 10-30% 
on surface tension measurements1. 
– Causes a decrease in surface tension
• Oxidation can occur at very low 
pO2
– Has been observed in the MSFC ESL as 
low as ~ 1x10-25 bar pO2
Calculated velocity and 
temperature fields for gas 
tungsten arc welding of 
pure iron and iron with 
0.03 wt% oxygen2.
The surface tension γ of 99.999% Ni 
as a function of pO2 measured by 
Schulz et. al2.
References:  
1. Ozawa, S., et. al., Influence of oxygen partial pressure on surface 
tension and its temperature coefficient of molten iron, Journal of 
Applied Physics, 2011, 109.
2. Schulz, M., et. al., Oxygen partial pressure control for microgravity 
experiments, Soliid State Ionics, 225, 2012, p. 332-336.
3. DebRoy, T. and S.A. David, Physical processes in fusion welding, 
Reviews of Modern Physics, 1995, 67(1), p. 85-112
5Supports Microgravity
• This system supports 
microgravity principal 
investigators:
– A similar oxygen control system is 
planned for the European Space 
Agency (ESA) International Space 
Station Electromagnetic Levitator 
(ISS – EML).
– Japan Aerospace Exploration 
Agency (JAXA) Electrostatic 
Levitation Furnace (ELF) that is 
planned to fly on the ISS
Sample inside of the ESA ISS-EML.
Schematic of the JAXA ELF electrode 
assembly.
6Hardware at MSFC
Oxygen Pump inside the levitation 
chamber.
Oxygen Sensor inside the levitation 
chamber.
• Developed by Astrium North America
• Fabricated by Clausthal University of 
Technology (TU Clausthal)
Stand-alone controller.
The system can also be controlled via 
computer software.
7Oxygen Sensing
• Potentiometric sensor
– Determines the difference in oxygen activity in 2 gas 
compartments separated by an electrolyte
• Yttria-stabilized zirconia (YSZ)
• Activity of gaseous compounds corresponds 
closely with their partial pressures
• The cell generates an electromotive force
– Difference in pO2 between the process gas and air, which is 
the reference gas
• pO2 is calculated by using the Nernst equation
– E = RT / 4F ln [ (pO2) / (pO2)^𝑟𝑒𝑓 ]
– E is the electromotive force
– R is the universal gas constant
– F is the Faraday constant
– (pO2)^𝑟𝑒𝑓 is the oxygen partial pressure of the reference gas 
(the lab atmosphere, in this case)
– pO2 is the oxygen partial pressure of the gas in question
Schematic of the oxygen sensor.  Ref:  Schulz, M., et al., 
Oxygen partial pressure control for microgravity 
experiments, Solid State Ionics, 2012, 225, p. 332-336.
8Oxygen Pumping
• Electric current is applied to the electrodes (Pt)
– Charge moved across the electrolyte in the form of oxygen 
ions, O2-
• Negative electrode
– Oxygen is incorporated into vacancies of the electrolyte, 𝑽𝑶
𝟎𝟎
• Positive electrode
– Oxygen leaves crystal lattice to form gaseous oxygen
• Must be operated above 500°C to enable sufficient 
ionic conductivity
Ref:  Ozawa, S., et al., Influence of oxygen partial pressure 
on surface tension of molten silver, Journal of Applied 
Physics, 2010, 107.
Schematic of oxygen ion pump
Oxygen molecules move through the YSZ 
tube from inside to outside when a difference 
in electrical potential is provided between 
the tube walls.
9Test Matrix
• Inconel 718
– Samples were made from rod stock
• Cut into small wafers by diamond saw
• Arc melted into spheroids
– Samples were cleaned with ethanol
• Sample processing only occurred after 
the oxygen partial pressure reached 
equilibrium.
• Melting caused the OPPC to change, but 
the OPPC eventually equilibrated
– Surface tension measurements were 
taken while the OPPC was changing and 
after equilibrated
• Oxygen partial pressures studied
– 10-12
– 10-18
• Surface tension measurements were made 
between 25°C above the melt point down to 
30°C below the melt point, including at the 
melt point
10
Example OPPC Plot
Oxygen partial pressure control over time.  Set to 10-18 bar. Zoomed into the sample heating region.  
11
Surface Tension vs. Temp
12
Conclusions and Future Work
• Preliminary results do not show a dependence on oxygen partial 
pressure.
• It is hypothesized that either there is no oxygen on the surface or that 
the oxygen partial pressure was not high enough to show a 
dependence.
– Measurements at higher oxygen partial pressures are planned.
13
Acknowledgements
• NASA Space Life and Physical 
Sciences Research and 
Applications (SLPSRA)
• NASA grant NNX16AB40G 
• Assistance running the 
experiments
– Trudy Allen and Glenn Fountain at 
MSFC


Effects of Oxygen Partial Pressure on the Surface Tension of Liquid Aerospace Alloys

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server