Super Alloy Nicrofer 4221 (UNS N08825)

Topics Covered

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

Introduction

Super alloys are high performance alloys meant for use in high temperature environments. They are strong and resist corrosion very well. Super alloy Nicrofer 4221 is a Ni-Cr-Fe alloy with additions of other alloying elements that is built specifically to resist chemical corrosion.

The following sections will discuss in detail about super alloy Nicrofer 4221.

Chemical Composition

The chemical composition of Nicrofer 4221 is outlined in the following table.

Element Content (%)
Nickel, Ni 38 - 46
Chromium, Cr 19.5 - 23.5
Molybdenum, Mo 2.5 - 3.5
Copper, Cu 1.5 - 3
Manganese, Mn 1 max
Titanium, Ti 0.6 - 1.2
Silicon, Si 0.5 max
Aluminum, Al 0.2 max
Carbon, C 0.05 max
Sulfur, S 0.03 max
Phosphorus, P 0.03 max
Iron, Fe Remainder

Physical Properties

The physical properties of Nicrofer 4221 are tabulated below.

Properties Metric Imperial
Density 8.13 g/cm3 0.294 lb/in3
Melting point 1385°C 2525°F

Other Designations

Equivalent materials to Nicrofer 4221 are listed below:

  • ASTM B163
  • ASTM B423
  • ASTM B424
  • ASTM B425
  • ASTM B564
  • ASTM B704
  • ASTM B705
  • DIN 2.4858

Fabrication and Heat Treatment

Machinability

Super alloy Nicrofer 4221 can be machined using the common processes applied to iron based alloys. This alloy does work-harden during machining and displays higher strength and "gumminess" unlike steels. It is recommended that heavy duty machining equipment and tooling should be used to reduce chatter or work-hardening of the alloy. Any common commercial coolant can be used during the machining operations. In case of high speed operations such as grinding, turning, or milling, it is best to use water-based coolants. Likewise it is advisable to use heavy lubricants for drilling, broaching, tapping, or boring.

Forming

Super alloy Nicrofer 4221 can be formed using any of the conventional methods as it is ductile. Since this alloy is stronger than regular steel it will requires a more powerful equipment to perform forming.

Welding

Welding of super alloy Nicrofer 4221 can be performed using all the traditional welding methods. Matching alloy filler metal should be used. In case that is not available, it is advised that the nearest alloy closest to the chemical composition be used. The weld beads should be slightly convex. Pre-heating is not required.

Hot Working

Hot working can be performed at temperatures less than 926°C (1700°F).

Forging

Forge at temperatures in the range of 1093-982°C (2000-1800°F). A final anneal is required to be performed at 954°C (1750°F) so as to regain optimum corrosion properties.

Cold Working

Nicrofer 4221 can be cold worked using all the standard tools.

Annealing

Nicrofer 4221 can be annealed at 954°C (1750°F) and rapidly cooled.

Hardening

Super alloy Nicrofer 4221 hardens only by cold work.

Applications

Nicrofer 4221 is used found in the following applications areas:

  • Pickling
  • Chemical process equipment
  • Acid production piping and vessels.

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