FUTURE RESEARCH TRENDS
No established ISO standard procedure is available till now for evaluation of materials and coatings for their hot corrosion resistance and hence the need to establish such standards in near future. In fact, the immediate concentration should be focused on this issue. Development of new alloys with a combination of experimentation, modelling and black art is necessary as further improvements in Ni-based superalloys are less possibility because the superalloys now operate at about 90% of their melting temperature. The future generation of high performance aerospace structures or potential candidate materials to replace superalloys are inter-metallic compounds, monolithic and composite ceramics, refractory alloys and research is needed in this direction. The developmental work should take place concurrently with coating system. Improved understanding of interfacial behaviour of TBCs and a more compatible hot corrosion / oxidation resistant bond coatings either by modification of chemistry or more stringent control of undesirable elements to control coating properties and to predict their performance is highly essential. Hence, the development of constructive life prediction modelling under simulated gas turbine engine conditions is necessary. Improved on-line control to ensure reproducible coated structures and within the service limits is also needed as increased improvements to current coating technologies are unlikely to meet the goals of future generation high performance turbine engines.
Then, development of Smart Coatings to combat type I & type II hot corrosion and high temperature oxidation for gas turbines is a challenging task to the Corrosion Engineer and developmental work in this area has lead to some smart coatings. Further research is highly essential for their understanding and to develop alternative smart coatings. Extensive research is needed both at the laboratory level and field to optimize coating composition, thickness, microstructure, identification of appropriate surface engineering techniques, and their priority of use and to prove their performance for manufacture of advanced gas turbine engines for exhibiting ever-greater efficiency.