Carbon vs tungsten as structural components in high temperature applications in an oxidative environment

So tungsten has a very high MP exceeding 3000°C. It's advocates use this high MP to promote tungsten as a material of choice for high temperature applications. But there is a problem. Tungsten exhibits this high MP behaviour only in an atmosphere where no oxygen in present. If oxygen is present it oxidizes rapidly after 500°C and loses its strength,cracks etc.

If we consider inert atmospheres, even carbon has a sublimation point of 3600°C and as long as its surface can be prevented from oxygen attack it's safe to use in high temperature environments.

If we consider oxidative atmospheres then like tungsten graphite can handle temperatures upto 500c. Some reports suggest even more upto 700c

Once tungsten has melted it would be of no use as a structural material though it can still be used as a coolant for extremely high temperature applications.

But if we consider terrestrial applications with reasonably high temperatures that are attainable in common use then carbon is a great choice once you can coat it with an anti oxidative layer.

Glass is a great choice for coating because it's silicon that has already been oxidised so further oxygen presence won't make a difference. Pure quartz glass can sustain temperatures of about 2500°C before its bonds break apart. At high temperatures it only softens and never melts.

https://akshatjiwannotes.blogspot.com/2024/12/low-energy-fabrication-of-high-strength.html

https://akshatjiwannotes.blogspot.com/2024/12/manufacturing-technique-for-layered.html

Even "impure" silicate glasses like soda lime and aluminium silicate can sustain more than a 1000 degrees (depending upon their composition)before they become viscous. That gives us a wide operating range of temperatures without having to deal with the peculiarities of mining ,extracting & refining tungsten.

References

https://www.sciencedirect.com/science/article/abs/pii/S0263436896000273

https://ia601309.us.archive.org/35/items/nasa_techdoc_19690026458/19690026458.pdf

https://www.reddit.com/r/Welding/comments/ublbg9/my_tungsten_keeps_getting_black_and_cracked/?rdt=37390

https://iopscience.iop.org/article/10.1088/0957-4484/19/16/16570

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Notes by Akshat Jiwan Sharma

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