Abstract
This paper presents hot corrosion results carried out systematically on the selected nickel based superalloys such as IN 738 LC, GTM-SU-718 and GTM-SU-263 for marine gas turbine engines both at high and low temperatures that represent type I and type II hot corrosion respectively. The results were compared with advanced superalloy under similar conditions in order to understand the characteristics of the selected superalloys. It is observed that the selected superalloys are relatively more resistant to type I and type II hot corrosion when compared to advanced superalloy. In fact, the advanced superalloy is extremely vulnerable to both types of hot corrosion. Subsequently, the relevant reaction mechanisms that are responsible for slow and faster degradation of various superalloys under varied hot corrosion conditions were discussed. Based on the results obtained with different techniques, a degradation mechanism for all the selected superalloys as well as advanced superalloy under both types of hot corrosion conditions was explained. Finally, the necessity as well as developmental efforts with regard to smart corrosion resistant coatings for their effective protection under high temperature conditions was stressed for their enhanced efficiency.
Highlights
Improved efficiency is the requirement for all types of modern gas turbines
It is observed that the selected superalloys are relatively more resistant to type I and type II hot corrosion when compared to advanced superalloy
After completion of hot corrosion tests, the specimens were examined for surface morphology with Scanning Electron Microscope (SEM) and the corrosion products were analyzed by Electron Dispersive Spectroscopy (EDS) and X-ray diffraction techniques
Summary
Achieving enhanced efficiency for marine gas turbines is a major challenge as the surrounding environment is highly aggressive This aspect depends on the design and on the selection of appropriate materials for their construction. Advanced materials with considerably improved properties are essential in order to enhance the efficiency of modern gas turbine engines. Efforts made in this direction made it possible to develop an advanced superalloy which exhibits excellent high temperature strength properties [1]. The hot corrosion resistance of superalloys is as important as their high temperature strength in gas turbine engine applications [5,6,7,8,9,10,11]. Comparative studies with an advanced superalloys were carried out under similar environmental conditions in order to determine the nature of degradation and to establish the possible reaction mechanisms that cause the selected superalloys to corrode under marine environmental conditions before suggesting suitable high performance protective coatings for their effective protection
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