SS304 steels have unique qualities and traits that demonstrate their usefulness in harsh environments. The primary problem with employing SS304 steel in shipbuilding and the maritime environment is cavitation erosion. Mo2C + CoNi is an appropriate candidate for adding a protective layer to SS304 steel using HVOF in such harsh surroundings in order to improve cavitation response. The mechanical properties of Mo2C + CoNi powder are improved by the addition of GNPs. In this article, SS304 steel was coated with Mo2C + CoNi + 3% GNP. Subsequently, cavitation testing was conducted with various impingement parameters, including jet velocity, stand-off distance, and impingement angle. The Vickers Indenter tester was used to measure micro-hardness. Steel coated with Mo2C + CoNi + 3% GNPs showed a cavitation response that was almost 1.5 times lower than that of SS304 base metal. The morphology and microstructure of the degraded surfaces were investigated using FE-SEM.