Metastable phase formation under lasre irradiation of nickel in caebon-containing atmosphere

An attempt is made to realize the synthesis of nickel carbide under the effect on the nickel surface of pulse-periodic CO2-laser radiation in propane atmosphere with 0.5 atm. pressure. The pulse energy constituted 2.3 J, pulse frequency 70 Hz, beam diameter 0.5 mm, pulse duration 5 μs. The electrolytic nickel plate displaced in relation to the beam with 0.09 cm/s rate which resulted in formation on the surface of several parallel ''laser tracks'' which have been subjected to radiography. It is shown that in the course of laser fusion of nickel surface in carbon-containing atmosphere two oversaturated solid solutions of carbon in nickel and two carbide phases with hexagonal close-packed structure and various specific volumes are formed. To each carbide phase an oversaturated solid solution with different carbon concentration in nickel corresponds and the less the carbide phase specific volume, the higher the solution oversaturation degree. The phase with a large specific volume is indiced as Ni3C and decayed at temperatures of 400-430 deg C