Thermodynamics of Simultaneous Chromizing-Aluminizing in Halide-Activated Cementation Packs
Abstract
The equilibrium partial pressures of the gaseous species in halide activated cementation packs have been determined with the computer program SOLGASMIX. The effects of the activator and the composition of the masteralloy on the coating process have been investigated. The activities of aluminum and chromium have been incorporated into the calculations and sodium chloride the results indicate that codeposition of Al and Cr is possible using sodium chloride, aluminum chloride or ammonium chloride as activators and Al-Cr masteralloys with compositions between 90 w/o and 95 w/o Cr. In contrasting the coating of nickel or iron substrates, the partial pressures of Ni halides are considerably lower than those of the Fe halides, indicating that displacement reactions occur when Fe substrates are coated. The upper limits for the surface composition of the coating have been predicted for different masteralloy compositions. Pack cementation is a modified chemical vapor deposition process carried out in a closed container at elevated temperatures (usually 1000 C). Aluminide, silicide and chromium coatings for hot corrosion and oxidation resistance are applied using this technique especially for aircraft turbine components.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1988
- Accession Number
- ADA197555
Entities
People
- P. Choquet
- R. A. Rapp
- V. A. Pavi
Organizations
- Ohio State University