Innovative Heat Treatment and Novel Non-Harmful Slurries for 'in situ' Aluminization or Co-Deposition of Elements on Steels for Corrosion Protection at High Temperatures

摘要

Aluminum surface enrichment is a common technique to reduce oxidation and corrosion of components made of Fe, Ni, and Co-base alloys. Due to their low cost and straightforward manufacture, slurry coatings are widely used to protect the surfaces of such alloys; however, they have three main disadvantages. First, salts such as phosphates, chromates or halides used as binders or to activate the diffusion species are toxic and harmful to the environment; secondly, the slurry coatings can only produce high activity coatings. Finally, these coatings are limited to the incorporation of Al and Si. For the first time an effective way to control the activity is presented by using common tempering temperatures for selected alloys and industrially relevant production times in combination with slurry technique and a careful design of the powder composition of the slurry and control of the diffusion process. These results extent the application range of slurry coatings, which previously could only be applied by more complex and expensive methods. Beyond that, these new coatings offer unique advantages such as a technique to repair coatings.