Use of a Mixture of Gases (C2H2 + N2) to Obtain High-strength Molybdenum-based Carbonyl Nitride Coatings

The effect of working pressure and the components correlation of the gas mixture (C2H2+N-2) to the elemental and phase compositions, the structure and physical and mechanical characteristics of the vacuum-arc coatings formed based on tungsten are studied. It is shown that for high-temperature application, nitrides are less preferable in comparison with carbides. In the temperature range of deposition 400-550 degrees C, the maximum content of nitrogen atoms in the coating does not exceed 1.5 at.% as a result of plasma-chemical reactions with a gas atmosphere composition of 80% C2H2+20% N-2. For a composition of 40% C2H2+60% N-2, the maximum N/C ratio (in at.%) increases to 10.5% at a maximum pressure of 3x10(-3) Torr. The relative content of nitrogen atoms increases with increasing pressure of the mixture. Plasma-chemical reactions during precipitation in a mixture of gases lead to the formation of phases with a nanometer-sized crystallite and a phase composition based on gamma-MoC (80% C2H2+20% N-2) and gamma-MoC and gamma-Mo2N phases (with a smaller content of C2H2 (40% C2H2+60% N-2) in the gas mixture It is established that the determining factor for increasing the hardness is the working pressure of the gas mixture during deposition. With the greatest pressure of 3x10(-3) Torr, when the texture of nanocrystallites of molybdenum carbide (gamma-MoC) is formed [100] an ultrahard state with a hardness of 50.5 GPa is achieved.