Ion-plasma saturation with interstitial atoms (nitrogen or carbon) is a promising method for enhancing the surface strength and wear resistance of austenitic stainless steel parts and products. The paper considers the influence of method and temperature of ion-plasma treatment (IPT) on phase composition, thickness, and strength properties (microhardness) of the surface layers in 01H17N13M3 austenitic stainless steel specimens. Steel specimens with a coarse-grained structure were nitrided in the arc and glow discharge plasma at different temperatures (400 °C, 550 °C, and 700 °C). Regardless of temperature and IPT-method, ion-plasma nitriding leads to the formation of hardened surface layers in steel specimens. In this case, the thickness and phase composition of IPT-hardened layers depend on both the method and temperature of nitriding. Nitrogen saturation of specimen surfaces in the glow discharge at a temperature of 400 °C promotes the formation of a thin S-phase layer (nitrogen-expanded austenite, 4 μm in thickness). At the same IPT temperature in the arc discharge plasma, the authors observed the formation of a heterophase (Fe-γN, Fe4N, CrN, and Fe-α) surface layer with a significantly greater thickness (40–45 μm). Regardless of the IPT-method, a saturation of specimens at temperatures of 550 °C and 700 °C is accompanied by the formation of thick heterophase hardened layers (40–60 μm). In this case, the IPT method has a negligible effect on the phase composition of layers but significantly affects the ratio of the volume content of the hardened phases. After being IPT-processed in different modes, the microhardness distribution profile for all specimens has three typical zones: a composite layer (or S-phase at the IPT in a glow discharge at Ta=400 °C), a diffusion zone, and a matrix. With an increase in the saturation temperature, the thickness of the transition diffusion zone increases regardless of the IPT method.
AN EFFECT OF ION-PLASMA NITRIDING ON THE MICROSTRUCTURE AND PHASE COMPOSITION OF ADDITIVELY-MANUFACTURED AISI 321 STAINLESS STEEL
