Federal-Mogul, Idaho National Laboratory and University of Florida.
This project involves both modeling and experimental study of stainless-steel alloys exposed to different corrosion atmospheres such as pure CO2 with and without addition of water vapor at high temperatures up to 800 °C. The main focus will be on the engine valves composed of valve steel alloys with high chromium concentration such as 21-2N and 23-8N illustrated in table below.
This part involves a development of a corrosion simulation tool named ‘SStAC’ (Stainless Steel Alloy Corrosion) that is based on a mechanistic corrosion framework that considers the impact of microstructure and alloy type on species transport and oxide growth. The corrosion model will be based on transport of species across the formed oxide layer, either through solid state diffusion (Coupled Current Charge Compensation point defect model) or molecular diffusion model (so-called ‘available space model’). The model will be fully validated with no more than 10% error against literature corrosion data, existing Federal-Mogul engine data, and new data collected in this project (see below) and will be ready to be used by industry for valve steel by the end of the project.
This part involves the characterization of the above mentioned alloys after corrosion in different atmospheres and at high temperatures and is divided into three campaigns.
The first campaign will determine how Austenitic stainless steel corrosion changes as a function of temperature, gas composition, and alloy type. The second campaign will determine the impact of grain size and chromium segregation on the corrosion. These studies are critical because in the literature there are conflicting reports on the influence of grain size and segregation on oxidation resistance. The final experimental campaign will focus on the impact of thermal cycling, since the majority of existing corrosion data is at constant temperature unlike the material in an engine environment that is constantly exposed to cycling temperature.