ABSTRACT:

Problems of create of high-temperature nickel alloys resistant to high-temperature corrosion in combustion products of low-grade fuel are considered. The relationship between the structure and properties of alloys and the alloying elements is studied. That provides high service characteristics of gas turbines. The obtained dependences are used to create new alloys resistant to high-temperature corrosion. Their structure and properties are described.

INTRODUCTION

The creation of new marine gas turbine engines (GTE) and gas turbine drives of power and gas-pumping units presupposes advance in their operating characteristics, i.e., power, service life, efficiency and reliability. Numerous researches and experience of long-term use of gas turbines have shown, that their power may be enhanced, basically, by rise of temperature of gas in front of the turbine. The reliability and service life of gas turbine parts depend to a great degree on the properties of their working capacity under the complex action of high stresses, temperatures, products of fuel combustion, and admixtures arriving from the ambient. Thus, the problems of increase of limiting temperatures of operation and service life of GTE parts will be always present. These problems are primarily solved by the use of high-temperature nickel alloys, especially for the hot duct of GTE. Nickel superalloys remain virtually indispensable materials for GTE blades despite the development of advanced ceramics. Deformable high - temperature nickel - base alloys earlier used in aircraft gas turbine engines (GTE) and have been replaced by cast alloys in the course improvement of the GTE design and the increase in the unit power and the gas temperature in front of the turbine. This resulted in the creation of turbine rotor blades and turbine vanes (guide blades) with a developed with allowance for the effect of oxidizing medium created by the combustion products of pure aircraft motor kerosene (alloys ZhS6K, ZhS26, Zhs6F, IN100, MarM200 and the like). The use of such materials for the production of parts of marine GTE and power and gas - pumping units (gaspipeline compressor units) has shown their inapplicability because of the occurrence of high - temperature corrosion (HTC) that intensifies under the effect of admixtures penetrating from the ambient (for example, sodium and chlorine from seawater)1, e.t.c.. Attempts to improve their resistance to high - temperature corrosion (HTC- resistance) by introducing a high amount of chromium caused a decline in their high - temperature strength. This increased considerably the probability of formation of topologically close-packed (TCP) phases that embrittle the alloys (VZhL18, EP539LM, EK9). USA -, EU - gas turbine industry use alloys of the type IN 738,Rene 80, IN939, which possess a good HTC resistance and a high - temperature strength. At the same time, the absence of a systematic and experimentally substantiated scientific approach to alloying of high - temperature nickel alloys resistant to HTC under the conditions in question hampered the development of such compositions. The available in literature on the effect of the alloying elements on the structure and properties of alloys are contradictory because they have been obtained for various model alloys.

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