11. METALLIC & NON METALLIC
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A. Incoloys, Inconels, Monel
A very important group of alloys is the nickel-based Inconels and Incoloys. These alloys have an excellent
resistance to a corrosive attack by many aggressive chemicals. They also have an excellent resistance to
oxidation at high temperatures and good high temperature strength. They typically contain 15-23% chro-
mium to provide a protective oxide flm. The Inconels contain 40-73% nickel, while the Incoloys contain
32-42% and 30-36% iron. Some grades contain a small amount of titanium or tantalum for improved high
temperature strength and aluminium to improve the protective characteristics of the oxide flm at elevated
temperatures (a mixed chromium oxide/aluminium flm).
Inconel 600
: High nickel 76%, high chromium 15.5%, for resistance to oxidizing and reducing at-
mospheres. I600 is used for several corrosive environments at high temperature.
Inconel 601
: High nickel 60.5%, high chromium 23.0%, plus 1.5% aluminium. Good high tempe-
rature properties. I601 provides an outstanding resistance to oxidation and a good
resistance to carburizing and sulphur containing atmospheres.
Incoloy 800
: 32.5% nickel, 46.0% iron, 21% chromium. Resistance to oxidation and carburization at
high temperatures. Resists sulphur attack and corrosion in many environments.
Incoloy 800H
: 32.5% nickel, 46.0% iron, 21% chromium. Resistance to oxidation and carburization at
high temperatures. Resists sulphur attack and corrosion in many environments.
Incoloy 800H
: A special version of the above alloy with a small controlled amount of carbon for impro-
ved high temperature strength.
Monel 400
: 66% high nickel, 31% high copper. Monel provides a good resistance to corrosion in
salt water. Not subject to chloride stress cracking. Monel is used for heat exchangers
and for sulphuric acid applications.
NICKEL BASED ALLOYS
THERMOWELL MATERIALS
B. Hastelloys
These nickel-based alloys are used for their excellent corrosion resistance under many severe conditions
due to their high molybdenum content.
Hastelloy B
: 61% nickel, 28% molybdenum. Excellent corrosion resistance to hydrochloric acid and
to sulphuric, phosphoric and acetic acids and hydrogen chloride gas.
Hastelloy C
: 54% nickel, 16% molybdenum, 15.5% chromium, 4% tungsten. Excellent corrosion
resistance to many chemical environments, including ferric acid and cupric chlorides,
contaminated mineral acids, and wet chlorine gas. Oxidation resistant to 1,900 °F.
Hastelloy X
: 47% nickel, 9% molybdenum, 22% chromium, 0.5% tungsten. Good high temperature
strength and resistance to oxidation to 2,200 °F. Also good for reducing conditions.