Coatings high-temperature corrosion

Diffusion alurninide and sihcide coatings on external and internal surfaces for high temperature corrosion protection in parts such as gas-turbine blades is estimated at 40 x 10 /yr in North America and about 50 x 10 worldwide. 

Turbine blades of jet engines are coated with a protective layer of platinum aluminide to impart high temperature corrosion resistance. Platinum is electroplated onto the blade using P-salt or Q-salt electroplating solutions (28,29). The platinum is then diffusion-treated with aluminum vapor to form platinum aluminide. Standards for the inspection and maintenance of turbine blades have become more stringent. Blades are therefore being recoated several times during their lifetime. 

The objective of surface modification by CVD is to develop additional corrosion protection for high-temperature alloys (e.g., Fe-25Cr-0.3Y) beyond that achieved by reactive-element additions which will be effective for a long period. Because CVD is a high temperature process, the following topics must be discussed before we can develop successful high-temperature corrosion-proteetion coatings. ... 

A durable protective coating for high-temperature alloys can be achieved by CVD. Normally, we must consider alloy stabilization in addition to chemical reaction in a controlled environment. The results define the nature of coatings for high-temperature corrosion protection, namely, a thin (1-2 pm) diffused silicon layer that covers the surface and penetrates even the smallest defects, cracks, etc., on the alloy to be protected. This surface modification treatment by CVD can be adapted to other alloys and is technologically simple and relatively inexpensive. 

Desmaison, J., 1990, High temperature oxidation of nonoxide structural ceramics use of advanced protective coatings, in High Temperature Corrosion of Technical Ceramics (RJ. Fordham, Ed.), Elsevier Applied Science, London, U.K., p. 93. 

Salto Y, Oenay B and Maruyama T (eds) 1992 High Temperature Corrosion of Advanced Materials and Protective Coatings (Amsterdam North-Flolland)... 

Fitzer, E., Schlichting, J. (1983), in High Temperature Corrosion Rapp, R. A. (Ed.). Houston National Association of Corrosion Engineers, pp. 604-614. Fitzer, E., Nowak, W, Maurer, H. J. (1978), in Materials and Coatings to Resist High Temperature Corrosion Holmes, D. R., Rahmel, A. (Eds.). London Applied Science, pp. 313-331. 

In diffusion coating, the substrate surface is enriched in an element that will provide high-temperature corrosion resistance. Typical elements are chromium (chromizing), aluminium (aluminizing), or silicon (siliconizing). The substrate is involved... 

Fig. 11.24 Effect of coatings on a titanium alloy in a high-temperature corrosive environment [34].

P. Yu, W. Wang, F. Wang, S. Zhu, High-temperature corrosion behavior of sputtered K38 nanocrystaUine coatings with and without yttrium addition in molten sulfate at 900 °C, Surf Coat. Tech. 206 (2011) 68-74. 

T. Sundararajan, S. Kuroda, J. Kawakita, S. Seal, High temperature corrosion of nanoceria coated 9Cr-lMo ferritic steel in air and steam. Surf Coat. Tech. 201 (2006) 2124-2130. 

M.A. Uusitalo, P.M.J. Uuoristo, T.A. Mantula, High temperature corrosion of coatings and boiler steels in reducing chlorine-containing atmosphere. Surf. Coat. Tech. 161 (2002) 275-285. 

F.J. Perez, E. Otero, M.P. Hierro, C. Gomez, F. de Pedtaza, J.L. Segovia, E. Roman, High temperature corrosion protection of austenitic AISI304 stainless steel by Si, Mo and Ce ion implantation. Surf. Coat. Tech. 108-109 (1998) 127-131. 

Materials Science and Engineering, A120/121, November 15, 1989, Proceedings, 2nd International Symposium on High Temperature Corrosion of Advanced Materials and Coatings, Les Embiez, France, May 1989. 

These initial results with hot-pressed samples indicate that phase transformations in high-temperature corrosive atmospheres are potentially complex. A better understanding of the phase chemistry under these conditions may be important in determining the performance of alumina-based coating systems, and of monolithic alumina or alumina matrix composites. 

Coatings used to protect gas turbines against high-temperature corrosion can be ... 

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