High Strength Peeled Inconel Alloy X-750 Nickel Alloy Products Open Die Forged

Product Specification

Forged high strength corrosion resistant Inconel alloy X-750 round bar

INCONEL® alloy X-750 (UNS N07750/W. Nr. 2.4669) 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 INCONEL 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. INCONEL 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 INCONEL alloy X-750. Other applications are heat-treating fixtures, forming tools, extrusion dies, and test machine grips. For springs and fasteners, INCONEL 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.

Chemical composition, %

Nickel (plus Cobalt)....................................................70.00 min.

Chromium...................................................................14.0-17.0

Iron..................................................................................5.0-9.0

Titanium.......................................................................2.25-2.75

Aluminum....................................................................0.40-1.00

Niobium (plus Tantalum)..............................................0.70-1.20

Manganese.................................................................1.00 max.

Silicon.........................................................................0.50 max.

Sulfur...........................................................................0.01 max.

Copper........................................................................0.50 max.

Carbon........................................................................0.08 max.

Cobalt1.........................................................................1.00 max

Corrosion Resistance

INCONEL 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.

Metallography

INCONEL alloy X-750, which contains aluminum and titanium, is made precipitation-hardenable by the combination, during heat treatment, of these elements with nickel to form gamma prime (γ’), the intermetallic compound Ni3 (Al, Ti).

When alloy X-750 is solution-treated at 2100°F, the number of dislocations and crystal defects are reduced, and γ’ and soluble carbides go into solution. For best results, the material should be in a fairly heavily worked condition prior to the treatment to ensure rapid and complete recrystallization. Once the material has been solution treated, it should not be subjected to any cold work since it will generate new dislocations and thus impair rupture properties.

Creep resistance of alloy X-750 stems from the uniform dispersion of intragranular γ’; whereas rupture properties are more closely related to grain-boundary area microstructure. During the 1550°F/24 hr stabilization treatment of the triple heat treatment, fine γ’ appears in the grain interiors and M23C6 is precipitated in the grain boundary; adjacent to the grain boundary is a zone denuded of γ’. On precipitation treating (1300°F/20 hr), γ’ has precipitated in this denuded zone. γ’ particles arrest the motion of moving dislocations, thereby increasing tensile and creep-rupture properties.

During M23C6 transformation at 1550°F, the carbon is essentially stabilized, without leaving chromium-depleted areas at the grain boundaries. This stabilization improves the resistance of nickel-chromium alloys to attack by certain corrosive media.

By lowering the precipitation temperature from 1350°F to 1150°F, as described for certain specific heat treatments, additional γ’ can be caused to nucleate in smaller particles, increasing the hardening effect and thereby improving tensile properties.

Available Products and Specifications

INCONEL alloy X-750 is designated as UNS N07750 and W. Nr. 2.4669. The alloy is stated in NACE MR-01-75.

Available product forms are round bar, flat bar, forging.

Specifications include the following:

Rod, Bar and Forging Stock - ASTM B 637/ASME SB 637; ISO 9723-9725; SAE AMS 5667-5671 and 5747; EN10269.

Product size range
Diameter: 100mm - 600mm
Length: on request
 
Production Process