Designing with Ni-Base Alloys

Abstract

Nickel (symbol Ni) is a very important and versatile element for major industrial metals. It is a vital alloying element in a wide variety of cast irons, steels, including austenitic stainless steels, and non-ferrous alloys. In addition, Ni-base alloys are used in numerous demanding applications which require corrosion resistance and high temperature strength (Figs. 1 and 2), and can also be used as coatings which exhibit these environmental resistance. Ni is also used in alloys with controlled thermal expansion or unique magnetic characteristics. Nickel, whose atomic weight is 58.71 and atomic number is 28, is a lustrous, silverywhite metal, and is one of the transition group of metals in the fourth series in the periodic table, with iron and cobalt. The melting point for Ni is 14538C and Ni has relatively low thermal and electrical conductivity, high resistance to oxidation and corrosion, excellent strength and toughness at elevated temperatures, as discussed in more detail below. In addition, Ni can be readily alloyed with many other metals. Nickel occurs in nature primarily as oxides, sulfides and silicates in numerous countries in all the continents. Primary Ni is produced and used in the form of ferro-nickel, nickel oxides and pure nickel metal. Nickel is also readily recycled in many forms and large quantities of secondary or scrap Ni are used to supplement newly mined metal. Typically, over 1 million tonnes of primary Ni is produced and consumed annually in the world, compared with over 800 million tonnes of steel [1]. Ni is widely used in consumer products, and in industrial, military, transportation, aerospace, marine, and architectural applications. Nickel is frequently used in coinage, and as an alloying addition to stainless steels and non-ferrous alloys. About 65% of Ni is used as an alloying addition to stainless steels and about 20% is used in other steels and non-ferrous alloys, including superalloys. About 9% of Ni is used for plating and about 6% is used for coins and nickel chemicals.