Tungsten carbide in 40% oxygen service

[dz84]

I am working with a customer whose system runs a mixture of different gases, one of them being 40% oxygen. We are using K500 Monel trim in our control valve, but because of the high pressures that the valve will experience, the customer wants the trim coated in tungsten carbide. Are there any concerns with using tungsten carbide in such a high concentration of oxygen?

 

[btrueblood]

Yes, I'd be concerned that it might create an ignition/fire. The stuff is fairly inert in air (21% oxygen), but that's also true for other stuff that burns rapidly in higher oxygen concentrations. There is a NASA RP (rp 1451)out there that discusses oxygen system design. There is a table on page 3-3 that shows tungsten carbide in 20% cobalt binder has a fairly high ignition potential in compressed oxygen, where the same table shows monels and similar alloys with much less risk.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19830024719.pdf