Ion Nitriding of Steels in a System with a Thermionic Gas Plasma Source

A study has been made into the method of ion nitriding of tool steels in the nitrogen plasma of arc discharge with a thermionic cathode. It is found that ion nitriding with a thermionic source of nitrogen plasma causes a considerably lower hydrogenation of steels than in the cases of gas nitriding in the presence of ammonia or ion nitriding in nitrogen-hydrogen mixtures in a glow discharge. The nitrogen concentration in subsurface layers of nitrided steels is 21 to 27 at.%. The process of ion nitriding lasted for 2 to 4 hours. After the process, the microhardness of carbon steel and alloyed steel surfaces increases by factors of 2 to 5. The greatest thickness of the hardened layer reaches 150 mu m. Steels studied: St30, U8A, 40Kh13, 5KhNM, R6M5 and R18.