Practical aspects of material data bases and expert systems for high-temperature corrosion and coatings in gas turbines

Abstract
High-temperature environmental attack often limits the useful service life of the hot section components in gas turbines, for aircraft, marine and industrial applications. High-temperature coatings are mandatory to obtain acceptable service life, but the life of these coatings often determines the refurbishment intervals. This paper addresses the use of computerized data bases and expert systems for high-temperature corrosion and high-temperature coatings, which have not always been useful for other material problems. The principal problems with material data bases are assessing the quality of the data ; describing the materials, test conditions and test results ; as well as the more common problems of data retrieval, correction of errors, and updating of data. Expert systems have generally not achieved expert performance, but are useful for people having less expertise than the program. Several expert systems are discussed including one that is currently being used by electric utilities to select high-temperature coatings for industrial gas turbine blades. Finally, in developing data bases and expert systems, the rapid prototyping process is recommended, along with a careful consideration of the end users, the available data and the available expertise.