Recuperation improves the efficiency of gas turbine engines by releasing heat from the exhaust gas stream and pre-heat the compressor to ejaculate air. The elevated temperature oxidation and creeping attacks are key problems that are driving the use of heat resistant alloys in the recuperator panels. Many modern recuperators are made of austenitic stainless steel foil. The water vapor existing in the exhaust gas as a side product of combustion is unfavorable to high temperature oxidation resistance, specifically for ferrous based alloys. The security layer of chromium oxide damages quickly in availability of water vapor because of the production of fast-developing iron oxide nodules. The increased magnitude of chromium and nickel seems to prevent the breakdown of oxidation layer. Inconel 625, a wrought Nickel-Chromium-Molybdenum superalloy strictly produced by HSM in the latest standards, is an eligible material for recuperator air cells. Experiments state that iron-chromium-nickel alloys containing higher percentages of chromium and nickel or low percentage of nickel increase oxidation resistance in the water vapor conditions.

Austenitic stainless steels do not contain sufficient chromium content to prevent corrosion of the base metal in the high temperature water vapor conditions. Such detrimental effect has given rise to the development of high alloy materials like nickel based super alloys to use in the applications where oxidation is extremely damaging in nature.

Heat resistant materials that depend on the production of chromium oxide to withstand against the elevated temperature oxidation can be prone to chromium loss due to the development of volatile compounds in availability of water vapor. Therefore low manganese percentage of the 625 alloy foil is suitable for playing a considerable role in improving the chromium evaporation.

During the tests, Alloy 625 foil samples subjected to the water vaporized air, attain nominal residual chromium levels, in fact it also performed well during the exposures that are conducted at the low temperatures where the influence of evaporation was not considerable in the oxidation weight change mechanism. Extensive chromium loss can cause the production of quickly developing oxides that refers to deleterious oxidation. The Inconel alloy 625 samples subjected to water vaporized air didn’t show a tendency towards the oxidation breakdown even while the intense exposures caused extensive chromium loss. Hence Nickel alloy 625 is excellently resistant to such kind of corrosion.

Contact HSM to get more information about the leading features of alloy 625.