Chromium corrosion resistant alloys

This is a high-carbon, high-chromium, corrosion-resistant alloy that can be described as either a high-hardness type 440C or a corrosion resistant, D2 tool steel. It possesses corrosion resistance equivalent to type 440C stainless but can attain a maximum hardness of Rockwell C 64, approaching that of tool steel. 

The two corrosion-resistant alloys presented ia Table 5 rely on chromium and molybdenum for their corrosion resistance. The corrosion properties of IJ1 timet are also enhanced by tungsten. Both alloys are available ia a variety of wrought product forms plates, sheets, bars, tubes, etc. They are also available ia the form of welding (qv) consumables for joining purposes. 

Stainless steels contain 11% or more chromium. Table 5.1 lists common commercial grades and compositions of stainless steels. It is chromium that imparts the stainless character to steel. Oxygen combines with chromium and iron to form a highly adherent and protective oxide film. If the film is ruptured in certain oxidizing environments, it rapidly heals with no substantial corrosion. This film does not readily form until at least 11% chromium is dissolved in the alloy. Below 11% chromium, corrosion resistance to oxygenated water is almost the same as in unalloyed iron. 

Hydrogen sulfide promoted corrosion can be a serious problem (150) the best solution is prevention. Corrosion problems can be minimized by choice of the proper grades of steel or corrosion resistant alloys, usually containing chromium or nickel (150, 151) and avoiding generation of H S by sulfate reducing bacteria in situations where H S is not initially present. Cathodic protection of casing is often effective for wells less than 10,000 feet deep (150). 

Disc and nozzle High corrosion-resistant alloy of chromium-nickel or nickel-chromium Ferritic steels not acceptable... 

Chromium Chromite [Fe(Cr02)2l Reduction of oxide by carbon Electroplating manufacturing corrosion-resistant alloy steels... 

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

In alloy steels, iron is mixed with carbon and varying amounts of other elements, mainly metals. Added metals produce desired properties such as hardness and corrosion resistance (Cr), resistance to wear (Mn), toughness (Ni), heat resistance (W and Mo), and springiness (V). Stainless steel is a well-known, corrosion-resistant alloy steel. It contains ten to 30 percent chromium and sometimes nickel and/or silicon. Because of its outstanding magnetic properties, Alnico steel is used to make permanent magnets. Alnico magnets are used in voltmeters and ammeters to rotate the cod of wire connected to the pointer. 

Nickel has a very small effect on the anodic polarization behavior of iron, and hence, iron-nickel alloys are of minor significance as corrosion-resistant alloys. However, the addition of nickel to iron-chromium alloys (AISI 200 series) permits conversion of the latter as ferritic alloys to austenitic iron-chromium-nickel alloys (AISI 300 series). In... 

Alloy Steels. These contain a iittie carbon, and sometimes siiicon, but they mainiy contain added metais, such as manganese (hardness), nickei (strength), moiybdenum (improved wear), tungsten (high temperature strength), chromium (corrosion resistance), and vanadium (toughness). 

The original conductor materials were stainless steel or platinum. These materials were later replaced with more corrosion-resistant alloys with improved fatigue resistance such as MP35N (SPS Technologies Cleveland OH), an alloy of nickel, chromium, cobalt, and molybdenum. In order to further reduce the resistance to current flow, specialized conductors were designed, including DBS (drawn brazed strand) and DFT (drawn filled tube)... 

The choice must be made between the use of more ejq)en-sive corrosion-resistant alloys, and the use of a less expensive, less corrosion-resistant alloys protected by chemical treatment. Chsuiges in the raw material costs of chromium, nickel, and other constituents in corrosion-resistant alloys affect the initial construction costs. A less expensive material, that would otherwise be unacceptable due to low corrosion resistance, can still be the best choice when used with chemical corrosion inhibitors, or other protection methods such as anodic or cathodic protection. 

About half of aU available chromium metal is used for the production of superalloys, that is nickel alloys with 15-20% chromium content, used for aero engines and other advanced purposes. The rest is mainly used for corrosion-resistant alloys other than stainless steels, for aluminum alloys and for hardfadng of alloys. The total world consumption of chromium metal was about 22 000 tonnes in the year 2002. That the USA consumed 40% of this can be expected because of its dominance in the world s aerospace industry. Europe is the second largest region, with about 33% of the total consumption. The major countries are the UK, Germany and France [24.2]. 

One of the most important attributes of nickel with respect to the formation of corrosion-resistant alloys is its metallurgical compatibility with a number of other metals, such as copper, chromium, molybdenum, and iron. A survey of the binary phase diagrams for nickel and these other elements shows considerable solid solubility, and thus one can make alloys with a wide variety of composition. Nickel alloys are, in general, all austenitic alloys however, they can be subject to precipitation of intermetallic and carbide phases when aged. In some alloys designed for high-temperature service, intermetallic and carbide precipitation reactions are encouraged to improve properties. However, for corrosion applications, the precipitation of second phases usually promotes corrosion attack. The problem is rarely encountered because the alloys are supplied in the annealed condition and the service temperatures rarely approach the level required for sensitization. 

This alloy is different from other corrosion-resistant alloys because it does not contain chromium. Molybdenum is the primary alloying element and provides significant corrosion resistance to reducing enviromnents. 

ALLCORR is a single phase, non-age hardenable, corrosion resistant alloy for service in highly corrosive environments. It is a nickel-base alloy containing nominally 31% chromium, 10% molybdenum, and 2% tungsten. It is characterized by the following properties ... 

Description and corrosion resistance. Alloy 800 is a nickel-iron-chromium alloy with good strength and excellent resistance to oxidation and carburization in high-temperature atmospheres. It also resists corrosion by many aqueous environments. 

Description and corrosion resistance. Alloy 600 is a nickel-chromium alloy designed for use from cryogenic to elevated temperatures in the range of 1093°C. The high nickel content of the alloy enables it to retain considerable resistance under reducing conditions and makes it resistant to corrosion by a nmnber of organic and inorganic compounds. 

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