The high temperature behavior of nickel based superalloys IN738, IN6 17, and CMSX-4 in pure steam and impure steam was investigated. Two kinds of experiment were carried out in this study. The first focused on the performance of superalloys IN738, IN61 7, and CMSX4 in high
temperature pure steam at 845, 875, 900, and 950°C. The results of this study were used to investigate the high temperature oxidation behavior of the superalloys induced by pure steam compared to those in air. The second dealt with the performance of these alloys in contaminated steam. In this case, two streams of steam carrying the salt impurities NaCl and Na2S04, passed through the internal bore of hollow cylindrical specimens of superalloys IN738, and IN617 housed in a firnace whose temperature was controlled at 875°C. One stream of steam was produced from water containing 5 ppm each of Na2S04 and NaCl salts while the second was from that containing 1 ppm of each salt. The temperature of steam in the internal passages of the tested specimens was estimated at about 225°C. This study was used to investigate the hot corrosion behavior of the tested superalloys induced by impure steam cooling. Thus in this paper, the performance of the superalloys in pure steam and impure steam at high temperature is examined, the mechanisms of the oxidation and corrosion of the superalloys induced by steam are briefly discussed, and suggestions are provided with regard to the application of steam cooling in land based gas turbine systems for power generation. Keywords: high temperature, oxidation, hot corrosion, land based gas turbine systems, superalloys, steam cooling