Modification of Surface Layers of Stainless Steel AISI 420 by a Combination of Thermal and Ultrasonic Impact Influence

The influence of ultrasonic impact treatment (UIT) on the microhardness, roughness and structural-phase state of the stainless steel AISI 420 surface is studied. Ultrasonic impact treatment is performed in an inert environment under the same conditions-the amplitude of the hub end was 25 mu m, the duration of treatment-50 s. Samples of AISI 420 steel are used after softening heat treatment at annealing temperature of 800 degrees C (initial state), after additional hardening from 980 degrees C with oil cooling and after additional hardening from 980 degrees C with subsequent annealing at 250 degrees C for one hour. As established, that after UIT there is a significant decrease in the roughness of the modified surface and increase in microhardness for all cases compared to the initial state. Taking into account the data of x-ray diffraction analysis the main factors of stainless steel AISI 420 surface layers deformation hardening under different combinations of thermal and ultrasonic impact are discussed.