In situ preparation of protective coatings for controlled nuclear fusion devices

Abstract

Thin Fe7C3 films were successfully prepared in an r.f. glow discharge using Fe(CO)5 and H2 as the gas source. The films showed a columnar crystal growth with a particle size less than 0.5 μm. The sheet conductivity of the films was in the range 1.0−5.0 × 104 ω−1 cm−1. The microhardness of the film on a glass substrate was 624.0 kgf mm−2. The Fe7C3 films formed on glass showed the presence of Fe7C3 and α-Fe phases after being annealed at 400 °C for 6 h. However, Fe3C (cementite) films formed on iron substrates. The influence of the H2O flow rate on the deposited films was investigated for both Fe(CO)5 + H2O and Fe(CO)5 + H2 + H2O systems.The plasma carburizing process was performed using either CO or a mixture of CO and H2 as the gas source and electrodeposited iron as the substrate. In the CO system, a carbon layer was formed as the main product while in the CO + H2 system, a homogeneous Fe3C film with a particle size of less than 0.5 μm and a microhardness of 479.0 kgf mm−2 was formed.