Why Inconel 600 is popular in high temperature and corrosion resistant valve?

Nickel-based alloy Inconel is widely used in the production of high temperature and corrosion-resistant valves. As specified in ASTM UNS N06600, the specified Inconel 600 is specified in ASTM A494 CY‐40. They are mainly used in stress corrosion resistant environments, especially for high concentration chloride media, when the Ni content is greater than 45%, it can be completely immune to chloride stress corrosion. In addition, it can resist the corrosion of boiling and concentrated nitric acid, fuming nitric acid, high-temperature gas containing sulfur and vanadium, combustion substances.

Inconel (ASTM B564 N06600) alloy is now widely used in boiler feedwater systems in nuclear power plants because it is safer than stainless steel. Inconel 600 or Inconel 625 high pressure (600 ~ 1500 LB) high concentration oxygen valves are commonly used in chemical fertilizer plants. The alloy valves of CY-40 and Inconel 600 take “In” as the material code, and the suitable operating temperature is -29~650℃.

The Inconel 600 has high strength and strong oxidation resistance at high temperatures. These alloys prevent stress corrosion cracking of metals caused by chloride ions in humid conditions. It is often used in large quantities in place of pure nickel to resist caustic corrosion and halogen corrosion at high temperatures, while not normally used in sulfuric acid units, but can be used at room temperature in low-concentration sulfuric acid media.

Inconel 600 has weak corrosion resistance to hydrochloric acid. It is resistant to all concentrations of pure phosphoric acid at room temperature, but the corrosion rate increases rapidly with increasing temperature. It also has good corrosion resistance to hot long chemical chain organic acids. Grease separation towers for stearic acid, oleic acid, and rosin acid are usually manufactured with Inconel 600 alloy.

The high Cr content of Inconel 600 alloy provides a good ability to prevent sulfur embrittlement. Therefore, it is often used in high-temperature alkaline media to replace Ni 201 containing S or where required high strength. Inconel 600, like all nickel alloys (except commercial pure Ni), is subject to stress corrosion when in contact with high temperature and high concentration alkaline media. Therefore, valves made of Inconel 600 should be completely stress-free before use to ensure minimal stress during operation.

Inconel 600 has good corrosion resistance to silver nitrate, also for optical processing and for hot, concentrated magnesium chloride. Inconel 600 was superior to Ni 200 in nitrite chlorides at temperatures greater than 43℃ (110 ℉). Inconel 600 can also be used in fasteners at 870 ° c (1 600℉) that require both high strength and oxidation resistance.

ASTM A494 specified CY-40 chemical composition and mechanical properties (table below) CY‐ 40 castings are usually supplied in as-cast condition and are not treated with the solution as the alloy is not sensitive to intercrystalline corrosion in the as-cast condition. It is suitable for industrial equipment which needs high strength, high pressure and closed state, has high corrosion resistance to chemical damage and harm, and has the ability to resist mechanical wear and oxidation under high temperature.

 

Chemical composition of CY-40, %

C max	Mn max	Si max	P max	S max	Cu	Mo	Fe max	Ni	Cr
0.40	1.50	3.00	0.03	0.03	/	/	11.0	Remind	14.0~ 17.0

 

The mechanical property of CY-40 

Tensile strength/MPa	yield strength/MPa	Elongation 50mm, %
485	195	30

 

Both of Inconel 600 and CY – 40 are high temperature and corrosion resistance of nickel-base alloy Ni ‐Cr‐ Fe alloy, their excellent properties of corrosion resistance to high temperature, high pressure make it widely used in the manufacture of nuclear industry or where need for high strength, high-pressure sealing, high corrosion resistance and high temperature resistant to mechanical wear and oxidation resistance of valve and equipment.