<p>This research investigates the influence of carbon content on the cavitation erosion behavior of three cast Fe-25Cr-5Ni duplex alloys containing 0.02, 0.12, and 0.37% C, respectively. The microstructure of these alloys comprises varying proportions of ferrite, austenite, and carbides, particularly present in the alloys with 0.12 and 0.37% C. Cavitation erosion tests were carried out following the ASTM G32 standard using a 20&#xa0;kHz transducer in distilled water. After testing, samples underwent microstructural examination by scanning electron microscopy. It was observed that ferrite loses mass due to the detachment of fragments assisted by cleavage, and the carbides also undergo fracture, but the mass loss due to the pull-out of fragments is smaller than in the case of ferrite. Conversely, austenite practically does not lose mass. As carbon increases the fraction of austenite, the higher the carbon content, the lower the mass loss presented by the Fe-Cr-Ni duplex alloys. The main technological implication is that materials with higher cavitation erosion resistance last longer, reducing the maintenance and replacement costs. This is relevant for pumps, turbines, propellers, and hydraulic machinery, where high-carbon cast Fe-25Cr-5Ni alloys are used.</p>