Development of an accelerated corrosion–erosion testing method for marine diesel exhaust valves using statistical experimental design

This paper addresses the problem of accelerated corrosion–erosion degradation of exhaust valves in marine diesel engines, caused by the combined effects of high temperature, aggressive sulfur compounds, and abrasive ash particles in combustion products. The main objective was to develop and validate a reproducible laboratory method that enables accelerated simulation of real operating conditions and quantitative assessment of the influence of individual factors on overall wear. A dedicated corrosion–erosion test chamber was designed to ensure precise control of sample surface temperature (650–800 °C), sulfur oxide (SOₓ) concentration, solid particle content, and other environmental parameters. The test specimens were exhaust valves from a 6ChN 18/22 engine, including both uncoated samples and those with heat-resistant protective coatings. To optimize testing and maximize information yield, a fractional factorial experimental design (2⁵⁻¹) was applied, enabling systematic evaluation of five key variables. After 100-hour test cycles, a comprehensive analysis was carried out, including measurements of wear rate, microcrack depth, mass loss, and microhardness changes. Analysis of variance (ANOVA) showed that surface temperature and SOₓ concentration exert the greatest influence on wear, with a pronounced synergistic interaction between SOₓ and solid particles. The experiments confirmed that fuel additives reduce chemical corrosion by 30–35 %, while protective coatings decrease erosive wear by 20–25 %. Validation of the developed method against field data demonstrated good agreement, with deviations within 10–15 %. The proposed methodology serves as an effective tool for predicting the service life of exhaust valves and justifying the selection of protective measures in marine engine design and shipbuilding practice.

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