High temperature corrosion of Ni₃Al intermetallic phase materials

Abstract

For several decades the ordered intermetallic phases have been of special interest for structural applications, because they combine good high temperature tensile strength with oxidation resistance even at high temperatures. Significant improvements in microalloying and metallurgical techniques have enabled an industrial production of Ni3AI. Examinations of the high temperature corrosion behaviour of this material were intended to give informations about potential applications. For this purpose the alloy was tested in the temperature range of 750°C to 1000°C in typical oxidizing, carburizing, sulfidizing and chloridizing environments. Time and temperature dependence of mass change were examined as well as the microstructural appearance of the specimens after the tests. The results show markedly improved oxidation, carburization and chlorination resistance, when compared with the commercial alloys 800 H and 617 while the sulfidation resistance of Ni3A1 is quite poor.Schon seit einigen Jahrzehnten sind die intermetallischen Phasen, und hier im besonderen die Aluminide, fur Konstrukteure von besonderem Interesse, da sie gute Warmfestigkeit mit Oxidationsbestandigkeit bei hohenTemperaturen in sich vereinen. Fortschritte in der Legierungstechnik und metallurgischen Verfahrenstechnik fiihrten zu Moglichkeiten, Ni3A1 auch industriell herstellen zu konnen. Untersuchungen des Hochtemperaturkorrosionsverhaltens dieser Legierung sollen AufschluB daruber geben, wo potentielle Einsatzgebiete der neuen Legierung sein konnten. Aus diesem Grunde wurde der Werkstoff im Temperaturbereich von 750 "C bis 1000 "C in typischen oxidierenden, aufkohlenden, sulfidierenden und chlorierenden Medien gepriift. Ermittelt wurden hierbei nicht nur Temperatur-und Zeitabhangigkeit der Gewichtsveranderung, sondern auch AS lichtmikroskopische Erscheinungsbild von Querschliffen der Proben. Die Untersuchungsergebnisse zeigen eine deutlich verbesserte Oxidations-, Aufkohlungs-und Chlorierungsbestandigkeit im Vergleich zu den kommerziellen Legierungen Alloy 800 H und Alloy 617, nur die Sulfidierungsbestandigkeit ist unterlegen.

Carburization Behavior of Electrodeposited Ni3 Al–CeO2-Base Coatings on Fe–Ni–Cr Alloys

“…13,14 The current trend is to develop Ni 3 Al or NiAl as novel carburizationresistant alloys or coatings. Brill 15 reported superior carburization resistance of Ni 3 Al base alloys in CH 4 -H 2 (a c = 0.8) to alloy 800H and alloy 617 at temperatures up to 1000°C. Commercial Ni 3 Al-base trays have been successfully adopted in industrial carburizing furnaces to replace those made of stainless steels, which often fail after six months.…”

High-temperature characterization of reactively processed nanostructure nickel aluminide intermetallics

“…However, considering the level of porosity initially present in the reactively fabricated nanostructure nickel aluminides before the high temperature characterization as shown in Fig. 1, the data presented here revealed very promising results compared to previous works [8,13,14,17,[22][23][24][25], this could be explained based on two combined factors:…”

“…Because of the potential use of nickel aluminides at high temperatures, it is imperative to understand and study their oxidation behavior. It was reported that the types of scale (oxide or mixture of oxides) and scale morphology formed on the surface of the alloy during high-temperature oxidation/or sulphidation were influenced by both the compositions of the gas and the alloy as well as the reaction temperature [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Both thermodynamic and kinetic factors should be considered to understand this complex corrosion process.…”

Carbon formation and metal dusting in advanced coal gasification processes

“…Nickel aluminides should be preferable to iron aluminides as alumina-forming alloys for metaldusting resistance because nickel is less reactive in the product gas environment, although it can exhibit a type of metal dusting in which a Ni-C solid solution decomposes directly without formation of an intermediate ~arbide?~ Nickel aluminides would not be suitable in the presence of H,S because they are very susceptible to sulfur-accelerated corrosion (see, for example, ref. 36).…”