IMPROVEMENT IN CAVITATION EROSION RESISTANCE OF X2CrNiMoN22-5-3 DUPLEX STAINLESS STEEL BY LASER BEAM NITRATION

Currently, one of the modern techniques for improving the surface properties of the stainless steel is the nitrating thermo chemical treatment. The research conducted in this paper aims at forming coatings with high hardness on the surface of Duplex stainless steel X2CrNiMoN22-5-3. This material was subjected to laser beam nitrating by using three pulse power regimes (240 W, 180 W, and 120 W). To highlight the effect of the behavior of the thermo chemical treatment upon details functioning in cavitation, for comparisons, there were used the results on the same steel, heat-treated only by quenching. The cavitation erosion resistance was highlighted by tracing erosion diagrams (expressing the variation of mass loss in time) as well as by the images of macro - and micro-system layer - substrate. The results showed that the change in the pulse power of the laser beam from 120 W to 240 W, lead to an increase in the depth of the nitrogen-enriched layer from 0.14 to 0.20 mm, at the same time increasing the resistance to cavitation with about 42 % if it is referred to the cumulative mass loss and by 35% when the erosion rate was taken into consideration.