Oxidation and mechanical performance of tungsten at high temperatures and high pressures.

The results of a study where tungsten and several composite tungsten systems were exposed to heat fluxes from 1015 to 4160 Btu/ft-sec at stagnation pressures from 21 to 70 atm and at stagnation temperatures from 5500° to 6750°R are presented. The test was conducted in the Cornell Aeronautical Laboratory wave superheater facility, where 39 specimens were tested. The variation of surface recession rate with heat-transfer coefficient was determined. Test results show that, in environments and structures where heat-transfer coefficients are less than 1.5 Ib/ft-sec and surface temperatures do not exceed 4000°R, the material is stable except for oxidation, which proceeds in a rate-con trolled manner. As the surface temperature rises above 4000°R, at heat-transfer coefficients up to 2.6 Ib/ft-sec and at stagnation pressure below 50 atm, surface recession occurs by diffusion-con trolled oxidation. When stagnation pressures exceed 50 atm, structural failure of the material occurs at the surface, and very high recession rates up to 0.1 in./sec are observed.