Performance of Alloy 625 under Combustion Gas Environments: A Review

Abstract

The nickel-based alloy 625 in the form of thermal sprayed coatings, as weld overlay, and as an alloyed material has been used extensively to minimize high temperature oxidation and hot corrosion in incinerators, supercritical water oxidation processes, biomass-fired plants, and other industries. Corrosion in these applications occurs due to the combination of gaseous species in the form of CO2, O2, SO2, and HCl; and solid impurities which form chlorides and sulphates of alkali and heavy metals (K, Na, Zn, Pb, Sn, etc) with low melting points. Even though alloy 625 has some shortcomings under certain conditions at high temperatures, the alloy from its beginning has had significant success, and its production has increased considerably worldwide. This paper will review some aspects for which alloy 625 is the material of choice and explain its unique features in many applications.