Super Alloy Haynes(r) X-750 alloy (UNS N07750)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal properties
Other Designations
Fabrication and Heat Treatment
     Machinability
     Forming
     Welding
     Heat Treatment
     Forging
     Hot Working
     Cold Working
     Annealing
Applications

Introduction

Super alloys contain a number of elements in a variety of combinations to obtain the desired result. They are also known as high performance alloys. Solid-solution hardening, precipitation hardening, and work hardening are performed for increasing the strength of super alloys. They have an ability to function under high mechanical stress and temperatures, and also where high surface stability is required. They are further classified into three types such as cobalt-based, nickel-based, and iron-based alloys.

Haynes(r) X-750 alloy is a nickel-chromium precipitation-hardening alloy. It has high ductility and excellent properties at cryogenic temperatures. The following datasheet provides more details about Haynes(r) X-750 alloy.

Chemical Composition

The chemical composition of Haynes(r) X-750 alloy is outlined in the following table.

Element Content (%)
Chromium, Cr 14-17
Iron, Fe 5-9
Titanium, Ti 2.25-2.75
Manganese, Mn 1 max
Niobium, Nb 0.7-1.2
Copper, Cu 0.5 max
Silicon, Si 0.5 max
Aluminum, Al 0.4-1
Carbon, C 0.08 max
Sulfur, S 0.01 min
Nickel, Ni Remainder

Physical Properties

The physical properties of Haynes(r) X-750 alloy are given in the following table.

Properties Metric Imperial
Density 8.26 g/cm³ 0.298 lb/in³
Melting point 1413°C 2575°F

Mechanical Properties

The following table shows the mechanical properties of Haynes(r) X-750 alloy.

Properties Metric Imperial
Tensile strength 1325 MPa 192.2 ksi
Elongation at break (in 51 mm) 23.60% 23.60%
Reduction of area 42% 42%

Thermal properties

The thermal properties of Haynes(r) X-750 alloy are displayed in the following table.

Properties Metric Imperial
Thermal expansion co-efficient (at 20-500°C/70-800°F) 14.3 µm/m°C 7.8 µin/in°F
Thermal conductivity (at 200°C/400°F) 14.1 W/mK 98 BTU in/hr.ft².°F

Other Designations

Other designations that are equivalent to Haynes(r) X-750 alloy include:

AISI 688 AMS 5598 AMS 5670 AMS 5747 GE B50TF1232
AMS 5542 AMS 5667 AMS 5671 ASTM B637 GE B50YP44
AMS 5582 AMS 5668 AMS 5698 DIN 2.4669 MIL N-24114
AMS 5583 AMS 5669 AMS 5699 DIN 2.4699 MIL N-7786
         

Fabrication and Heat Treatment

Machinability

Haynes(r) X-750 alloy can be machined using conventional machining methods, which are used for iron-based alloys. Machining operations are performed using machining coolants. High-speed operations such as grinding, turning, or milling, are performed using water-base coolants. Drilling, broaching, tapping, or boring are performed using heavy lubricants.

Forming

Haynes(r) X-750 alloy can be formed using all conventional techniques.

Welding

Haynes(r) X-750 alloy is welded using shielded metal-arc welding, gas-tungsten arc welding, gas metal-arc welding, and submerged-arc welding methods.

Heat Treatment

Haynes(r) X-750 alloy is heat treated by annealing at 885 to 1149°C (1625 to 2100°F).

Forging

Haynes(r) X-750 alloy is forged at temperatures ranging from 1205 to 1038°C (2200 to 1900°F).

Hot Working

Haynes(r) X-750 alloy is hot worked at temperatures ranging from 983 to 1038°C (1800 to 2200°F).

Cold Working

Haynes(r) X-750 alloy can be cold worked using standard tooling. Soft die materials such as bronze and zinc alloys, are used for providing good finish and reducing galling problems.

Annealing

Haynes(r) X-750 alloy is annealed at 983 to 1038°C (1800 to 2000°F) followed by cooling.

Applications

Haynes(r) X-750 alloy is mainly used in structural members of hot sections of gas turbines such as ducts, thrust reversers, discs.

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