Depending on the formulation of the plating solution, commercial coatings may contain 6 to 12% P dissolved in nickel, and as much as 0.25% of other elements. Hypophosphite-reduced electroless nickel is one of the very few metallic glasses used as an engineering material. This combination of properties makes the coating well suited for many severe applications and often allows it to be used in place of more expensive or less readily available alloys. They can be precipitation hardened to very high levels through the use of low-temperature treatments, producing wear resistance equal to that of commercial hard chromium coatings. As applied, nickel-phosphorus coatings are uniform, hard, relatively brittle, lubricious, easily solderable, and highly corrosion resistant. These metals have excellent resistance to thermal creep deformation and retain their stiffness, strength, toughness and dimensional stability at temperatures much higher than the other aerospace structural materials.Hypophosphite-reduced electroless nickel is an unusual engineering material, because of both its method of application and its unique properties. Nickel is the base element for superalloys. Nickel also reduces thermal expansion for better dimensional stability. Nickel and its alloys are highly resistant to corrosion in many environments, especially those that are basic (alkaline). Fe-Cr-Ni(Mo) alloys) alloys exhibit excellent ductility and toughness, even at high strength levels and these properties are retained up to low temperatures. Nickel is used as a constituent of different types of alloys for instance, Monel (corrosion resistant material), Nichrome (an alloy used for resistance heating elements), Permalloy (an alloy with high magnetic permeability at low field strength and low hysteresis loss), cupro-nickel, stainless steel, nickel silver, etc. The global production of nickel is presently used as follows: 68% in stainless steel 10% in nonferrous alloys 9% in electroplating 7% in alloy steel 3% in foundries and 4% other uses (including batteries). The mechanical properties are sensitive to the content of carbon, which is normally less than 1.0 wt%. There are thousands of alloys that have different compositions and/or heat treatments. Due to its very-high strength, but still substantial toughness, and its ability to be greatly altered by heat treatment, steel is one of the most useful and common ferrous alloy in modern use. Adding a small amount of non-metallic carbon to iron trades its great ductility for the greater strength. Steels are iron–carbon alloys that may contain appreciable concentrations of other alloying elements. Since pure iron is quite soft, it is most commonly combined with alloying elements to make steel. Its low cost and high strength often make it the material of choice material to withstand stress or transmit forces, such as the construction of machinery and machine tools, rails, automobiles, ship hulls, concrete reinforcing bars, and the load-carrying framework of buildings. Iron is the most widely used of all the metals, accounting for over 90% of worldwide metal produc0tion. Iron is used in numerous sectors such as electronics, manufacturing, automotive, and construction and building.
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