Superalloy Properties and Facts
1. When temperatures are above 1000oF or 540oC, general steel and titanium alloys are not much stronger for use. The steel materials may attain corrosion.
2. When the maximum temperatures lower than melting temperatures are about 2200 to 2500of or 1204oC to 1371oC for several alloys should be obtained and strength is also essential, then nickel base superalloys are materials of preference.
3. Nickel based superalloys such as Inconel 718 are utilized to a larger fraction of melting points than about any other commercially made materials. The refractory metals possess higher melting point as compare to superalloys however they don’t offer equivalent properties as superalloys and are less popularly employed.
4. Cobalt base superalloys can be employed in lieu of nickel based superalloys, based on real strength requirements and the kind of corrosion believed.
5. At the lower temperatures and based on the kind of strength required for an operation iron-nickel based superalloys have more applications than cobalt or nickel superalloys.
6. The strength characteristics of superalloys are directly linked to the composition of an alloy however also to the melting points, forging and working procedures, casting techniques and most importantly forming, forging or casting.
7. Iron-nickel base superalloys like Inconel 718 are less costly than nickel or cobalt base superalloys.
8. Many wrought superalloys sufficiently have high magnitudes of chromium to offer corrosion resistance. In cast alloys,chromium was sufficiently high earlier but highly decreased within a period to accumulate other elements that improved the high temperature strength of superalloys. In the superalloys made of nickel, content of aluminum increased if chromium content reduced. Hence, the oxidation resistance of nickel materials remained almost constant to basic levels or in fact enhanced. Although resistance to other kind of corrosions attack reduced.
9. Superalloys offer high oxidation resistance,in several conditions, however not sufficient corrosion resistance. In the various applications that are conducted at the very high temperatures above 1400of or 760oC as in aerospace turbines, superalloys should be coated. For extensively longer applications at the high temperatures above 1200oF or 649oC such as in land based gas turbines, the coated superalloys are used.
10.Coating technology is an essential part of superalloy development and use. Insufficient coating refers to lower ability to use superalloys for prolong periods at the high temperatures.
11.Several compositional elements are included to superalloys in small to large extents, specifically in nickel based alloys.
12.Nickel and cobalt as well as chromium, tungsten, molybdenum, rhenium, hafnium and other elements utilized in superalloys are usually costly and strategic elements that may change significantly in price are introduced over time.