The surface of ships and other marine transportation equipment is eroded by sandy seawater when running.With the change of the speed of ships,cavitation erosion will occur.Because seawater has corrosive effect on metal materials,the damage forms of surface materials of ships are combined wears for slurry erosion,cavitation erosion and corrosion.In order to study the influencing factors of the combined wear,an experimental set up for combined wears was developed.The effects of sand concentrations,sand sizes,salt concentrations and impact speed on the combined wear of steel 45 were studied experimentally.The results show that the combined wear for slurry erosion,cavitation erosion and corrosion is stronger than the interactive wear for slurry erosion and cavitation erosion or the simple corrosion wear.Under the conditions of lower sand concentration and lower salt concentration,the mass loss of metal materials for combined wears is proportional to the sand concentration,sand size,salt concentration and impact speed.The analysis of wear surface morphology shows that with the increase of sand concentration,sand size,salt concentration and impact speed,the depth and area of wear marks of erosion ditches and cavitation holes on the surface of specimens are increased.In artificial seawater,there are not only erosion ditches and cavitation holes on the surface of specimens,but also corrosion pits.