Super Alloy Nicrofer 5621 (UNS N06022)

Topics Covered

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

Introduction

Super alloy Nicrofer 5621 is a wrought nickel-chromium-molybdenum alloy with the addition of tungsten for improved overall corrosion resistance. It was designed as an alternative to alloys 625 and C-276.

Nicrofer 5621 has excellent metallurgical stability and good resistance to localized corrosion. It is not sensitized during welding or heating operations.

The following sections will discuss in detail about super alloy Nicrofer 5621.

Chemical Composition

The chemical composition of Nicrofer 5621 is outlined in the following table.

Element Content (%)
Chromium, Cr 20 - 22.5
Molybdenum, Mo 12.5 - 14.5
Iron, Fe 2-6
Tungsten, W 2.5 - 3.5
Cobalt, Co 2.5 min
Manganese, Mn 0.5 max
Vanadium 0.35 min
Sulfur, S 0.02 max
Phosphorus, P 0.02 max
Silicon, Si 0.08 max
Carbon, C 0.015 max
Nickel, Ni Remainder

Physical Properties

The physical properties of Nicrofer 5621 are tabulated below.

Properties Metric Imperial
Density 8.6 g/cm3 0.314 lb/in3
Melting point 1399°C 2550°F

Other Designations

Equivalent materials to Nicrofer 5621 are listed below:

  • ASTM B366
  • ASTM B564
  • ASTM B574
  • ASTM B575
  • ASTM B619
  • ASTM B622
  • DIN 2.4602

Fabrication and Heat Treatment

Machinability

Super alloy Nicrofer 5621 can be machined using high-speed steel tooling for drilling operations. For turning or milling operations it is best to use carbide tools. It is possible to machine this alloy dry or with conventional coolants

Forming

Super alloy Nicrofer 5621 can be easily cold or hot formed using any of the conventional methods. It is recommended that after hot forming or rigorous cold forming, the parts should be solution heat treated.

Welding

Welding of super alloy Nicrofer 5621 can be performed using most of the traditional welding methods except submerged arc welding. The areas to be welded should be cleaned properly. It is recommended that matching filler metals ER NiCrMo-10 and E NiCrMo-10 should be used for GTAW and SMAC methods, respectively.

Forging

Forging should be performed at 1148°C (2100°F). It is recommended that a solution heat treatment should be performed after forging.

Hot Working

Hot working can be performed on this alloy; however it must be followed by a solution anneal heat treatment.

Cold Working

Nicrofer 5621 can be easily cold formed using all the standard tools as it is very ductile.

Annealing

Nicrofer 5621 can be solution annealed at 1121°C (2050°F) and rapidly quenched.

Aging

Nicrofer 5621 can be aged at temperatures ranging from 510-1037°C (950-1900°F) to enhance the hardness and tensile strength. Aging at temperatures above 760°C (1400°F) causes degradation of V-notch impact strength.

Applications

Nicrofer 5621 is mainly used in the chemical industry. Nicrofer 5621 is used in many applications as listed below:

  • Flue gas scrubbers
  • Chlorination systems
  • Sulfur dioxide scrubbers
  • Pulp and paper bleach plants
  • Acid production and pickling systems
  • Outlet ducting and stack liners for power plants
  • For weld overlay of less corrosion resistant metals.

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