Super Alloy HAYNES 718 (UNS N07718)

Topics Covered

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

Introduction

Super alloy HAYNES 718 is a high-strength, high-temperature resistant and corrosion resistant nickel-chromium alloy. This alloy provides excellent high-temperature strength of up to 650°C (1202°F), formability, weldability, and good ductility. The following sections about super alloy HAYNES 718 will be discussed in detail below. 

Chemical Composition

The chemical composition of HAYNES 718 is outlined in the following table.

Element Content (%)
Nickel, Ni 52
Iron, Fe 19
Chromium, Cr 18
Niobium, Nb 5
Tantalum, Ta 5
Molybdenum, Mo 3
Cobalt, Co ≤ 1
Titanium, Ti 0.90
Aluminum, Al 0.50
Manganese, Mn ≤ 0.35
Silicon, Si ≤ 0.35
Copper, Cu ≤ 0.10
Carbon, C 0.050
Boron, B 0.0090

Physical Properties

The physical properties of HAYNES 718 are tabulated below.

Properties Metric Imperial
Density 8.23 g/cm3 0.297 lb/in3

Mechanical Properties

The following table shows mechanical properties of HAYNES 718.

Properties Metric Imperial
Tensile strength 1395 MPa 202300 psi
Yield strength 1175 MPa 170400 psi
Elastic modulus 200 GPa 29000 ksi
Elongation at break 22.3 % 22.3 %

Thermal Properties

The thermal properties of HAYNES 718 are tabulated below.

Properties Metric Imperial
Thermal expansion co-efficient (at 25-200°C/77-392°F) 12.8 µm/m°C 7.11 µin/in°F
Thermal conductivity 11.4 W/mK 79.1 BTU in/hr.ft².°F

Other Designations

Equivalent materials to HAYNES 718 are tabulated below:

AMS 5589 AMS 5832 ASTM B637 GE B50TF14 GE B50TF15
AMS 5590 AMS 5664 ASTM B670 GE B50 TF69 PWA 1009
AMS 5596 AMS 5663 DIN 2.4668 GE B14H89 PWA 1010
AMS 5597 AMS 5662 DIN 2.4688 GE B50 TF14 PWA 1033
RBO 170-153 SPS M275 SPS M637    

Fabrication and Heat Treatment

Machinability

HAYNES 718 can be machined using the common processes used for iron based alloys. The material work hardens during machining and has higher strength and gumminess. It is recommended that heavy duty machining equipment and tooling be used to reduce chatter. Commonly available commercial coolants can be used for the process.

Forming

HAYNES 718 can be readily formed using all the traditional methods. As this alloy has high strength, powerful equipment has to be used. It is important that the material is properly cleaned of all traces of lubricant after forming to prevent embrittlement from occurring.

Forging

Forging can be done at 1121-926°C (2050-1700°F).

Welding

Welding of HAYNES 718 can be performed using all the traditional welding methods. It is recommended that a matching alloy filler metal be used. Preheating is not required. The surfaces to be welded have to be free from oil, paint or crayon markings.

Annealing

Annealing of the material can be performed at 1037°C (1900°F) and then rapidly air cooled.

Hot Working

Hot working can be performed by heating the alloy to 1121-899°C (2050-1650°F). The alloy has to be reheated if hot working temperatures drop below 899°C (1650°F).

Cold Working

HAYNES 718 can be cold worked using all the traditional methods and tooling.

Aging

For aging HAYNES 718, anneal at 982°C (1800°F) and age at 718°C (1325°F) for 8 h. This should be followed by furnace cooling to 621°C (1150°F) and holding at that temperature for 10 h, and then air cooled.

Applications

HAYNES 718 is used in the following application areas:

  • Cryogenic storage tanks
  • Gas turbine hot section components
  • Fasteners and instrumentation parts
  • Various components for oil/gas well down holes and well heads
  • Aircraft and land-based turbine engine components such as rings, casings, and formed sheet metal components.

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