Alloy X-750

UNS N07750, Alloy X-750, W.Nr.2.4669, GH4145

Alloy X-750 is a precipitation-hardenable nickel-chromium alloy used for its corrosion and oxidation resistance and high strength at temperatures to 1300°F. Although much of the effect of precipitation hardening is lost with increasing temperature over 1300°F, heat-treated material has useful strength up to 1800°F. Alloy X-750 also has excellent properties down to cryogenic temperatures.

The economics of alloy X-750 coupled with its availability in all standard mill forms has resulted in applications in a wide variety of industrial fields. In gas turbines, it is used for rotor blades and wheels, bolts, and other structural members. Alloy X-750 is used extensively in rocket-engine thrust chambers. Airframe applications include thrust reversers and hot-air ducting systems. Large pressure vessels are formed from alloy X-750. Other applications are heat-treating fixtures, forming tools, extrusion dies, and test machine grips. For springs and fasteners, alloy X-750 is used from sub-zero to 1200°F.

Depending on the application and the properties desired, various heat treatments are employed. For service above 1100°F, particularly where loads are to be sustained for long times, optimum properties are achieved by solution treating (2100°F) plus stabilization treating (1550°F) plus precipitation treating (1300°F). For service below 1100°F, the alloy may be strengthened by precipitation treating after hot or cold working or by precipitation treating after equalizing or solution treating. A furnace-cooling treatment is also used to develop optimum properties for some applications.
Due to its high temperature strength up to 820 °C (1500 °F) and its excellent corrosion resistance, Alloy X-750 finds a wide range of applications.

Alloy X-750 is resistant to a wide variety of industrial corrosives under both oxidizing and reducing conditions. It resists oxidation and attack by other high-temperature corrosion mechanisms.
In hot corrosion tests for automotive applications, weight loss after exposure for 100 hours in 90% Na2SO4 + 10% NaCl mixture in air was about 5%. Samples precoated with sodium chloride (by dipping in a hot saturated salt solution), suspended in a furnace at 1700°F and exposed for 100 hr to a moving gas stream of air containing 1% SO2 exhibited a corrosion penetration of approximately 0.007 in. An interesting feature of this alloy is its high resistance to chloride-ion stress-corrosion cracking even in the fully precipitation-hardened condition. Standard U-bend specimens of precipitation-hardened material (hardness, 33 Rc) showed no signs of cracking when exposed to boiling 42% magnesium chloride for 30 days.

Cold worked and bright annealed

Cold worked, bright annealed, polished (MP, EP etc.)

Capillary tube

• _◎ OD 0.30 ~ 3.0 mm
• _◎ WT 0.05 ~ 0.5 mm

Precision seamless tube

• _◎ OD 3.0 ~ 89 mm
• _◎ WT 0.10 ~ 10.0 mm

HP / UHP BA+ tube

• _◎ OD 3.0 ~ 76 mm
• _◎ WT 0.10 ~ 10.0 mm