Thermochemical treatment of tungsten and molybdenum in the flow of rarefied atomic hydrogen under action of radiant energy

Thermochemical treatment of tungsten monocrystal samples with the (110) crystallographic plane taken out to surface was carried out at the SGU-5 solar installation. It is show that mechanical properties of metall can be improved, when the annealing temperature of samples in hydrogen is considerably lower and the gas is preliminarily atomized (up to ∼ 25%) in high-frequency discharge. Cast molybdenum of electron-beam melting susceptible to brittle intergranular fracture were annealed at 680-1100 K temperatures. It was found that the cold brittleness temperature of the samples decreased from 473 to 333 K, i.e. by 140 K. It was observed that after annealing at 1070 K the cold brittleness temperature of cast tungsten slightly decreased from 593 to 563 K. This insignificant drop of the cold brittleness temperature of tungsten was evidently related to formation of impurity element hydrides (P, S, N, C, Si) in the surface layer, which final desorption was hindered under the experimental conditions (p=26.6 Pa). Reannealing of the samples in vacuum 1.33x10-4 Pa at the same temperature leads to much more intensive decrease of the cold brittleness temperature of tungsten down to 453 K