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 CO 2 , O 2 , SO 2 , 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.

Microstructure and Phase Analysis of Multilayer Ni–Cr–Mo Clad for Corrosion Protection

“…The nickel-based alloys can be strengthened by solid-solution hardening, precipitation hardening or both. Because of the considerable expense of Ni in Inconel alloys, these alloys are not economically feasible to be used as bulk materials and are usually used as welding materials in overlay welding [1,2].…”

The potential use of laser cladded functionally graded materials to mitigate degradation in boiler tube heat exchangers for power plant applications: A review

“…This is attributed to the phase transformation that occurs when the laser beam interacts with the substrate causing pearlite to dissolve and form a martensitic structure in the heat-affected zone. Cracking can also occur in the HAZ if the laser power is low because segregation of impurities will be hindered during deposition [64,65]. This confirms that heat exchanger tubes made of carbon steel excel in corrosion resistance due to the presence of chromium, iron, and manganese.…”

“…On the other hand, In625 is also reported to perform best in waste-to-energy-fired boilers, especially in the temperature range of 400°C-650°C. It effectively prevents high-temperature oxidation and corrosion when operating at elevated temperatures due to high content concentration of Nb, Mo, and Cr, which often form a protective layer of Cr 2 O 3 , including NiO, Nb 2 O 3 , and NbCrO 4 [65]. Hruska et al [52] investigated the corrosion behaviour of nickel-based coatings at elevated temperatures.…”

Corrosion Damage Behavior of X65/Incoloy 825 Welded Bimetallic Composite Pipe in H2S Environment

“…However, Nb and Mo will be dispersed into liquid metal during the solidification of Inconel 625 weld metal and then enriched in the intergranular region to form intermetallic compounds named Laves phases (Silva et al, 2013), which tends to cause pitting corrosion (Xu et al, 2013). Due to the depletion of Ni and Cr, the protective effect of the passivation film is weakened, and the corrosion mainly occurs in the intergranular region (Bakare et al, 2010;Cuevas-Arteaga et al, 2010). Ahmed and Cooper thought that the local corrosion mechanism of the Inconel 625 weld was related to the galvanic corrosion between dendrites (Laves phase) (Cooper et al, 1996;Ahmed et al, 2010).…”