Incoloy alloys, corrosion

To overcome this corrosion problem, nickel-based super alloys such as Inconel alloy 625 and Incoloy alloy 864 have been used. Although these alloys are more costly than stainless steel, they have shown excellent corrosion resistance in the modern automotive exhaust environment. 

As an alternative to X-750 the equally age hardening alloys Inconel 718 (2.4667), Incoloy alloy 925 (UNS N09925), Incoloy alloy 926 (UNS N09926) as well as the non age hardening alloys Inconel 600 (2.4816), 625 (2.4856) and in particular Inconel 690 (2.4642) were tested for their behaviour to stress corrosion cracking and hydrogen embrittlement under the conditions of a boiling water reactor, see Table 12 [162]. 

It is important to know whether or not the alloy is resistant to crevice corrosion. For instance, work on the various grades of steels, such as SS 304, carpenter alloy, Incoloy (Alloy 825), Hastelloy (Alloy g), and Inconel (625) showed that the later two alloys were highly resistant to crevice corrosion in ambient and elevated temperature seawater [6]. The alloying elements in various grade of steel affect both the electrochemical and chemical processes, such as hydrolysis, passive film formation, passive current density and metal dissolution. Hence, the effect of major alloying elements, such as Fe, Cr, Ni and Mo and... 

Regarding future work, CJuantiamis investigating the hot erosion-corrosion properties of other furnace alloys such as 300 series stainless steels. Inconel and Incoloy alloys. Further research will also be conducted on the synergistic relationship between hot erosion wear and corrosion. This work will include... 

Raymond, E. L., Mechanism of Sensitisation and Stabilisation of Incoloy Nickel-lron-Chromium Alloy 825 , Corrosion, 24, 180 (1968)... 

Replacing some of the nickel with iron produces a family of alltws with intermediate corrosion resistance between stainless steels and the Ni-Cr-Mo alloys. Alloys such as Incoloy 825 and Hastelloy G-3 and G-30 are in this family. Incoloy 825 has 40 percent Ni, 21 percent Cr, 3 percent Mo, and 2.25 percent Cu. Hastelloy G-3 contains 44 percent Ni, 22 percent Cr, 6.5 percent Mo, and 0.05 percent C maximum. These alloys have extensive applications in sulfuric acid systems. Because of their increased nickel and molybdenum contents they are more tolerant of chloride-ion contamination than are standard stainless steels. The nickel content decreases the risk of stress-corrosion cracking molybdenum improves resistance to crevice corrosion and pitting. Many of the nickel-based alloys are proprietary and are coverecf by the following specifications ... 

The most important applications of nickel metal involve its use in numerous alloys. Such alloys are used to construct various equipment, reaction vessels, plumbing parts, missile, and aerospace components. Such nickel-based alloys include Monel, Inconel, HasteUoy, Nichrome, Duranickel, Udinet, Incoloy and many other alloys under various other trade names. The metal itself has some major uses. Nickel anodes are used for nickel plating of many base metals to enhance their resistance to corrosion. Nickel-plated metals are used in various equipment, machine parts, printing plates, and many household items such as scissors, keys, clips, pins, and decorative pieces. Nickel powder is used as porous electrodes in storage batteries and fuel cells. 

Cr content in all these alloys helps to passivate the metal surface. Among all the different candidates, Incoloy 800H has shown the best performance, with a corrosion rate of less than 100 pm/yr after a 9,000-h test at 900°C. AISI310 was jndged to be applicable to lower-temperature application. ... 

Incoloy [Inco], TM for a series of corrosion-resistant alloys of nickel, iron, and chromium. 

The above indicates that low alloy steel, e.g. IViCr ViMo, can be used for most loop equipment including the converter pressure shell. Critical parts are the reactor internals (the basket ), which are most often made fi om stainless steel (SS 321), and the inlet part of the waste heat boiler which must either be made from or cladded by corrosion-resistant material, like Incoloy or similar. 

Inconel-625, Incoloy 800) perform better than stainless steel, but still significant corrosion occurs in the presence of HCl, H2SO4 and HNO3, or HF, HBr or HI. Oxidants such as O2 and H2O2 enhance the corrosion of many alloys (stainless steel, Ni-base alloys ). Some improvement is possible by adding Ti, Zr or Al/Nb/Ti to steels. Also, iron-free but very expensive metals like pure titanium or zirconium,or alloys like Monel (Ni- -Cu) and Ti60 have been tested. 

CU5MCuC is the cast version of Incoloy 825 (trademark of Inco Alloys Intemational) although columbium is substituted for titanium. Titanium will oxidize rapidly during air melting columbium will not. CU5MCuC has corrosion resistance and weldability similar to CN7M. It has equal corrosion resistance in sulfuric, nitric, and phosphoric acids, seawater, and other environments. It is also highly resistant to chloride SCC. 

These alloys represent another version of Ni-Cr-Fe alloys and contain 30-44% of nickel. Alloy 800 of this series has been extensively used in heat exchangers in the petrochemical industry, because of its excellent resistance to stress corrosion cracking in chloride environments and cracking in polythionic acid. It offers an excellent resistance to creep and rupture. They are used for high environments where resistance to oxidation and corrosion is required. Incoloy 825 has proved highly successfiil in applications in H2SO4, HCl, phosphoric acid and clean and polluted seawater. 

Although nickel alloys on the whole offer a better resistance to stress corrosion cracking over the steels, their application in high temperature chloride or alkaline environment and hydrogen sulfide environment may put them to the risk of stress corrosion cracking. Cases of SCC have been observed in high temperature pressurized water in steam generating turbines. Incoloy 800... 

Alloy 800 series are derived from Incoloy 800, originally developed in the 1950s by the International Nickel Company [18]. AUoy 800 series have high nickel and chromium contents which give them superior resistance to corrosion in many kinds of environments (Table 17.2). Titanium and aluminum additions lead to the precipitation of different carbonitrides which enhance the material properties. But this Ti + A1 content also leads to the precipitation of hard y Ni3(Ti,Al) phase which enhances creep resistance but decreases the material ductility at high temperature. This is why the Ti + A1 content has been limited in some specifications (800 HT, 800 SPH). On the other hand, annealed material was historically differentiated from solution annealed material, with the terms grade 1 annealed at approximately 980°C, and grade 2 solution annealed at approximately 1150°C [19]. 

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