The Influence of Induction Hardening, Nitriding and Boronising on the Mechanical Properties of Conventional and Sintered Steels

Heat treatment technology changes all the mechanical properties of metallic materials. The influence of induction hardening, nitriding and boronising on the change in the microhardness, impact toughness, microstructure and coefficient of friction of conventional steels 42CrMo4 and 32CrMo12 has been examined and compared with results obtained in the sintered steels with an increased content of Cu, which were prepared using powder metallurgy technology. Widely used treatments for the examined materials include induction hardening and gas nitriding. This study focuses on comparing those technologies with alternative technologies of boronising. It was found that for powder metallurgy materials, boronising is a much more suitable process than nitriding because after the application of nitriding, the impact toughness dropped to one third of the impact toughness of the base material, while after boronising, the impact toughness remained unchanged. Through boronising, it was possible to achieve the unique possibility of improving the mechanical properties of sintered PM Fe-Cu-C steels and fully replacing the currently used nitriding process. Furthermore, compared to nitriding, it also increases the hardness of the surface layer many times to improve the friction properties and significantly increases the impact toughness.