Expect of high-fluence low energy nitrogen ions implantation on structure and properties of high-speed steel

Effect of the high-fluence low energy nitrogen ions implantation on structure and properties of high-speed steels (R6M5 and R18) was studied. Experiments were performed using the facility with a triode gas plasma source based on thermionic cathode arc discharge ignited in nitrogen atmosphere. The nitrogen ions implantation into steel specimens surface was carried out an energy of 0.6 keV. The irradiation doses ranged from 5 10¹⁹ to 10²⁰ ion/cm². The temperature of implanted specimens was not above 500°C. Studies were made into the structure, composition and microhardness of implanted high-speed steel specimens. Metallographic, X-ray diffraction and electron-microscope methods were used to investigate the surfaces of implanted specimens. It is found that microhardness of implanted steel specimens surface increases by factors of 1.6 to 1.7. The thickness of the strengthened layer reaches 120 μm. The bulk of the material exhibits practically no unstrengthening after low energy nitrogen ions implantation. The nitrogen concentration in subsurface layers of implanted high-speed steels is 21 at.%. The X-ray diffraction analysis performed for implanted steels points the presence of Fe₂N, Fe₂N+Fe₄N or Fe₄N nitrides and the carbide phase