Nickel-iron-based alloys

With cobalt historically being approximately twice the cost of nickel, cobalt-base alloys for both high temperature and corrosion service tend to be much more expensive than competitive alloys. In some cases of severe service their performance iacrease is, however, commensurate with the cost iacrease and they are a cost-effective choice. For hardfaciag or wear apphcations, cobalt alloys typically compete with iron-base alloys and are at a significant cost disadvantage. 

The resistance of a metal to erosion-corrosion is based principally on the tenacity of the coating of corrosion products it forms in the environment to which it is exposed. Zinc (brasses), aluminum (aluminum brass), and nickel (cupronickel) alloyed with copper increase the coating s tenacity. An addition of V2 to 1)4% iron to cupronickel can greatly increase its erosion-corrosion resistance for the same reason. Similarly, chromium added to iron-base alloys and molybdenum added to austenitic stainless steels will increase resistance to erosion-corrosion. 

Although iron sulphide also forms a eutectic with the metal this melts at 988°C, and at temperatures in the region of 700 to 800°C alloys with substantial proportions of nickel replaced by iron and a chromium level maintained at about 20% show advantages over nickel-chromium-base alloys in resistance to sulphur attack. 

Table 7.33 Corrosion rack tests of nickel- versus iron-base alloys used in waste incineration...

Researchers have tried to fabricate plates using many different metals— mainly, stainless steel, aluminum alloys, titanium alloys, nickel alloys, copper alloys, intermetallic alloys, and metal-based composites such as carbon fiber-reinforced aluminum alloys, carbon fiber reinforced copper alloys, etc. [26]. Although Ta, Hf, Nb, Zr, and Ti metals show good corrosion resistance and chemical stability [6], the cost of fhese metals is too high for them to be used as materials in metal plates. That is why relatively cheaper iron-based alloys, particularly stainless steel, have been popularly studied as plate material. In the following secfions, we will infroduce sfainless sfeel (SS) and SS plates, which have been extensively investigated and show promise for the final applications [6,11]. 

High-purity metals and superalloys are required for the aeronautics, electronics, instruments, space, and defense industries the raw materials are at present imported. Primarily, these special metals include nickel-and cobalt-based superalloys, high-strength iron-based alloys, titanium-based alloys, controlled-expansion alloys, and magnetic materials. Keeping in view the importance of these metals and alloys and the expertise available in India for making them, the NCST has identified two projects for their development the setting up of a special metal and superalloys plant and the development of controlled-expansion alloys. 

Discaloy [Westinghouse], TM for an austenitic iron-base alloy containing nickel, chromium, and relatively small proportions of molybdenum, titanium, silicon, and manganese. This alloy is precipitation-hardened and was developed primarily to meet the need for improved gas-turbine disks, one of the most critical components of jet engines. 

Nickel-iron-chrome alloys include the iron base superalloys and the heat resistant castings (see previous section). Iron-base superalloys are an extension of the austenitic stainless steels and include alloys such as the Incoloy 800 series. They are used for piping and manifolds in refining, power generation and petrochemicals. 

Brasses and bronzes, iron-base alloys, nickel, monel, magnesium alloys, hard rubber, plastics, tin, aluminum, and like metals must be added to ordinary gray and white cast iron as materials for pump construction. Practically any alloy or modern metal can be fabricated into pumps, and it remains only for the chemical engineer to stipulate the kind of solution he wishes to handle, or the kind of metal, and the pump manufacturer will attempt to construct a pump for the service demanded. (See Perry s Chemical Engineers Handbook, 3d ed., p. 1424.)... 

The history of these intriguing materials goes back to 1938, when A. Oleander observed the shape memory ability of An—Cd and Cu—Zn alloys (Wayman and Harrison, 1989). Later on other materials such as indium-, nickel-, titanium-, and iron-based alloys were shown to have similar behaviour (Reardon, 2011). Unlike other shape memory alloys, Ni—Ti in particular was found to be very resistant to corrosion and/or degradation and hence ideally suited to implantation in a range of applications, including the human body, albeit more expensive than its other counterparts. Hence the very first temperature-dependent shape memory alloys to be commercialised were nickel—titanium (Bogue, 2009). 

Corrosion of Stainless Steels in Acids Stainless steels are iron-based alloys with chromium as the main alloying element. The most interesting alloys for technical applications are ferritic stainless steels, austentic stainless steels, and duplex stainless steels. The distinction between the stainless steels comes from their different crystallographic structures. Ferritic-martensitic stainless steels and martensitic stainless steels have less nickel and a higher carbon content and can be hardened by heat treatment. The corrosion behavior of these steels is mainly influenced by the formation of carbides, which generally increase the corrosion rate. 

The nickel-base alloys, C-4, C-276, and 625, are resistant to HSC in the heavily cold-worked condition (48% and higher) [184]. Aging these alloys, however, markedly decreases their resistance to HSC. The decrease in some cases may be related to grain boundary segregation of phosphorus [185]. Tests on two nickel-base alloys (600 and 690) together with two iron-base alloys (321 and 800) that contain nickel have shown... 

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