Super Alloy Nicrofer 5219 Nb (UNS N07718)

Topics Covered

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

Introduction

Super alloys are exceptionally strong and lightweight. These alloys display excellent mechanical strength, creep resistance at elevated temperatures, good surface stability, corrosion and oxidation resistance, thus making them capable of surviving in extreme conditions that would basically destroy base metals like aluminum and steel.

Nicrofer 5219 Nb is a high-strength, high-temperature resistant and corrosion resistant nickel-chromium alloy. It is can be used at cryogenic temperatures and also in air up to 704°C (1300°F). This alloy can be readily worked and age-hardened. The following sections will discuss in detail about super alloy Nicrofer 5219 Nb.

Chemical Composition

The chemical composition of Nicrofer 5219 Nb is outlined in the following table.

Element Content (%)
Nickel, Ni 50 – 55
Chromium, Cr 17 - 21
Niobium (Nb) 4.75 - 5.5
Molybdenum, Mo 2.8 - 3.3
Cobalt, Co 1 max
Titanium, Ti 0.65 - 1.15
Silicon, Si 0.35 max
Manganese, Mn 0.35 max
Copper, Cu 0.3 max
Aluminum, Al 0.2 - 0.8
Carbon, C 0.08 max
Phosphorus, P 0.015 max
Sulfur, S 0.015 max
Boron, B 0.006 max
Iron, Fe Balance

Physical Properties

The physical properties of Nicrofer 5219 Nb are tabulated below.

Properties Metric Imperial
Density 8 g/cm3 0.29 lb/in3
Melting point 1326°C 2420°F

Thermal Properties

The thermal properties of Nicrofer 5219 Nb are tabulated below.

Properties Metric Imperial
Thermal conductivity (@20°C/68°F) 11.1 W/mK 77 BTU in/hr.ft².°F

Other Designations

Equivalent materials to Nicrofer 5219 Nb are given below:

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

Fabrication and Heat Treatment

Machinability

Super alloy Nicrofer 5219 Nb 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 commercial coolants can be used during the machining operations; however water-based coolants are recommended for high-speed operations such as milling, turning, or grinding. Similarly, heavy lubricants are ideal for tapping, broaching, drilling, or boring.

Forming

Super alloy Nicrofer 5219 Nb can be formed using any of the conventional methods. Powerful equipment is required to perform forming operations as this alloy is strong.

Welding

Welding of super alloy Nicrofer 5219 Nb 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.

Hot Working

Hot working can be performed in the temperature range of 1121-899°C (2050-1650°F). In case the hot working temperatures fall below 899°C (1650°F), it is essential to reheat the alloy.

Forging

Forging can be performed at temperatures in the range of 1121-927°C (2050-1700°F).

Cold Working

Nicrofer 5219 Nb can be cold formed using all the standard tools.

Annealing

Nicrofer 5219 Nb can be annealed at 1037°C (1900°F) and rapidly air cooled.

Hardening

Super alloy Nicrofer 5219 Nb hardens by cold working and aging heat treatment. Cold working increases both hardness and strength of this alloy.

Aging

For aging super alloy Nicrofer 5219 Nb, the material has to be annealed at 982°C (1800° F) and aged at 718°C (1325°F) for 8 h. Then furnace cooled to 621°C (1150°F) and held at that temperature for 10 h, and finally air cooled. This treatment provides the highest room temperature strength and excellent rupture properties.

Applications

Nicrofer 5219 Nb is widely used in many application areas as listed below:

  • Pump shafts
  • High-strength bolting, springs and fasteners
  • Turbine disk material in aircraft jet engines
  • Drilling equipment in sour oil and gas wells
  • Components in nuclear reactors and space vehicles
  • Gas turbine hot section components and cryogenic storage tanks
  • Highly stressed rotating and static components in gas turbines and rocket engines
  • High-temperature tooling for extrusion of metals such as copper, and for shearing
  • Highly stressed well head and downhole parts in offshore and marine engineering.

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