In this study, cavitation erosion tests were conducted to investigate the effects of the presence of coolant additives and chlorides on the corrosion and cavitation erosion of cylinder liners in marine diesel engines. Electrochemical experiments were conducted to evaluate the corrosion characteristics of ductile cast iron (DCI), and the corrosion potential and corrosion current density were measured. In addition, weight loss, surface roughness, and maximum surface damage depth were quantified as a function of cavitation exposure time. Furthermore, to investigate the erosion and erosion–corrosion characteristics induced by cavitation attack, the damaged surface morphology was closely examined using a scanning electron microscope (SEM) after the cavitation erosion tests. The results revealed that the coolant additive effectively protected the DCI from corrosion caused by aggressive chlorides. In particular, when an appropriate amount of additive was added to a coolant containing 100 ppm of chloride, the corrosion current density of DCI was reduced by approximately 31.7 times, significantly improving corrosion resistance. Therefore, different surface damage mechanisms corresponding to cavitation erosion and cavitation erosion–corrosion were identified depending on the presence or absence of the coolant additive during the cavitation erosion tests.

This study investigates the degradation characteristics of turbocharger nozzle rings in marine diesel engines by conducting numerical analysis and solid particle erosion (SPE) tests to examine their structural stability and morphological surface damage trends. The fatigue analysis was conducted under a load condition corresponding to 100% output of the main engine, using ANSYS software. The SPE test was conducted in accordance with ASTM G76-05 standards, and the weight loss and erosion rate were calculated. Surface damage was closely examined through 3D analysis and scanning electron microscopy (SEM). The flow analysis revealed that the loads were highly concentrated at the nozzle ring inlet and the leading edge of the blades, with a maximum pressure coefficient of 0.07678 MPa. The load decreased toward the trailing edge of the nozzle ring, and the surface pressure coefficients of the flange, inner hoop, and outer hoop—where the nozzle ring blades are fixed—were found to be nearly identical. The fatigue life of the nozzle ring under 100% engine load was calculated as 1.377e⁺⁷ cycles, with a fatigue damage value of 1.32e⁺³². Notably, the fatigue life in the regions near the inner and outer hoops of the nozzle ring approached zero. The results of the SPE test using spherical SiO₂ particles confirmed that the surface damage of the nozzle ring material, 316L stainless steel, followed a typical ductile material damage mechanism. In addition, the surface damage characteristics were significantly influenced by SPE test parameters such as the shape of solid particles, nozzle diameter, and impact angle.