Land-based Gas Turbines Research Articles

Coating service experience with industrial gas turbines

Abstractield experience with high–temperature coatings on land–based gas turbine blades and vanes is reviewed. The article covers all relevant coatings such as the chromium type, precious metal aluminides, and overlay coatings of the NiCrSi and MCrAlY (M = Fe, Co, Ni) types. Long term service behaviour, allows, various guidelines to be drawn for the selection of a coating appropriate to particular operating conditions. In the low–temperature hot–corrosion regime, high chromium containing coatings appear to be the most effective and the aluminides less so. At higher temperatures, aluminides are superior and offer protection comparable to that given by MCrAlY overlays. The advantage of these overlays lies in a higher compositional flexibility, especially when deposited by low–pressure (vacuum) plasma spraying. Service performance can be significantly affected by the mechanical integrity of the coatings; some ductility is required to accommodate thermal stresses. A general lifetime prediction for coatings is...

Growth Limitations of the Japanese Superalloys Industry

Top-of-the-line structural metallic systems consist of critical and strategic superalloys. These vacuum melted, multicomponent alloys are “super” because they are heat resistant and maintain reasonable strength to high temperatures. At present, the United States leads in the research, development, and production of these alloys, primarily used in the hot turbine sections of jet engines and stationary gas turbines.1 This could change, however, since Japan is trying to become a world leader in the manufacture of jet engines and landbased gas turbines and, by necessity, superalloys.

Experience with platinum aluminide coatings in land-based gas turbines

Hot-corrosion crucible tests with salt mixtures which simulated actual blade deposits were carried out to evaluate the potential of platinum-modified aluminide coatings for application in advanced industrial gas turbines. In comparison with simple aluminide coatings, a significantly improved resistance against hot corrosion at intermediate temperatures was found. At the highest turbine-operating temperature, coating life exceeds that of conventional plasma-sprayed NiCrSi coatings. Actual engine test results are presented which confirm the beneficial role of platinum. However, the susceptibility of platinum aluminide coatings to crack formation and propagation may make them unsuitable for application to rotating blades.