Grey Super Alloys

Super alloys are important in high temperature applications; hence, they are also known as heat-resistant or as high-temperature alloys. Image source: Nuclead Applications: Major applications of this alloys are in reciprocating engines, in rocket engines, in tools and dies for hot-working of metals and in the nuclear, chemical and photochemical industries. Properties: They generally have good resistance to corrosion, to mechanical and thermal fatigue, to mechanical and thermal shock, to creep and to erosion at higher temperatures. Composition: These alloys are referred to as iron-base, cobalt-base or nickel-base super alloys. They contain nickel, chromium, cobalt and molybdenum as major alloying elements; Most super alloys have a maximum service temperature of about 1000°C for non-load bearing components. Iron base super alloys generally contain composition of 32% to 67% iron, from 15% to 22% chromium and from 9% to 38% nickel. Cobalt-base super alloys generally contain composition of 35% to 65% cobalt, 19% to 30% chromium and up to 35% nickel. Cobalt (Co) is white-colored metal that resembles nickel. These super alloys are not as strong as nickel-base super alloys in this they retain their strength at higher temperatures. Nickel-base super alloys are the most common of the supper alloys and they are available in a variety of compositions. The composition of nickel is from 38% to 76%; they also contain up to 27% chromium and 20% cobalt. Common alloys in this group are the Hastelloy, Inconel, Nimonic, Rene, Udimet, Astroloy and Waspaloy series.