Super Alloy Discaloy™ (UNS S66220)

Topics Covered

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

Introduction

Super alloys or high performance alloys have an ability to function at very high temperatures and mechanical stress, and also where high surface stability is required. They have good creep and oxidation resistance, and can be produced in a variety of shapes. They can be strengthened by solid-solution hardening, work hardening, and precipitation hardening.

Super alloys consist of a number of elements in a variety of combinations to achieve the desired result. They are further classified into three groups such as cobalt-based, nickel-based, and iron-based alloys.

Discaloy™ is an age-hardenable alloy containing chromium and nickel as the principle alloying element. The following datasheet gives an overview of Discaloy™.

Chemical Composition

The chemical composition of Discaloy™ is outlined in the following table.

Element Content (%)
Nickel, Ni 24-28
Chromium, Cr 13-15
Molybdenum, Mo 2.5-3.5
Titanium, Ti 1.5-2
Manganese, Mg 1.5 max
Silicon, Si 1 max
Copper, Cu 0.5 max
Aluminum, Al 0.35
Carbon, C 0.08
Phosphorus,P 0.04 max
Sulfur, S 0.03 max
Boron, B 0.01-0.001

Physical Properties

The following table shows the physical properties of Discaloy™

Properties Metric Imperial
Density 7.7-8.03 g/cm³ 0.278-0.290lb/in³
Melting point 1455°C 2650°F

Mechanical Properties

The mechanical properties of Discaloy™ are displayed in the following table.

Properties Metric Imperial
Tensile strength 1158 MPa 167954 psi
Yield strength 1034 MPa 149969 psi
Elastic modulus 190-210 GPa 27557-30458 ksi
Poisson's ratio 0.27-0.30 0.27-0.30
Elongation 15% 15%
Reduction 53% 53%
Hardness 335 335

Thermal Properties

The thermal properties of Discaloy™ are given in the following table.

Properties Conditions
T (ºC) Treatment
Thermal conductivity 42.7 W/mK 100 -

Other Designations

Other designations that are equivalent to Discaloy™ include:

  • AMS 5733
  • ASTM A453 (662)
  • ASTM A638 (662)

Fabrication and Heat Treatment

Machinability

Discaloy™ is machined using conventional machining methods which are used for iron-based alloys. It has machining properties similar to that of austenitic stainless steels. Work-hardening of this alloy can be reduced by using a heavy duty machining equipment and tooling. Water-based coolants are used in machining operations.

Forming

Discaloy™ is formed using conventional techniques.

Welding

Discaloy™ is welded using gas tungsten arc welding, shielded metal-arc welding, and metal-arc welding methods. Submerged-arc welding is not preferred for this alloy. Slag should be completely removed using a wire brush after completing this process.

Heat Treatment

Discaloy™ is heat treated by annealing and cold working.

Forging

Discaloy™ has good forgeability.

Cold Working

Discaloy™ can be cold worked using standard tooling. Soft die materials such as zinc alloys and bronze are used to produce good finishing and reduce galling problems.

Annealing

Discaloy™ is annealed at 1010°C (1850°F) for 2 h followed by quenching in oil.

Aging

Discaloy™ is aged by annealing at 1010°C (1850°F) for 2 h followed by quenching in oil, and then at 733°C (1350°F) for 20 h followed by cooling in air, and finally at 649°C (1200°F) for 20 h followed by cooling in air.

Applications

Discaloy™ is mainly used in gas turbine hot section components.

Comments

  1. sumbal Nazir sumbal Nazir Islamic Republic of Pakistan says:

    fracture toughness? creep strain? rupture stress?

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