Nov 15 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
Machinability
Forming
Welding
Heat Treatment
Cold Working
Annealing
Hardening
Applications
Introduction
Super alloys comprise a number of elements in a variety of combinations to achieve the desired result. They have high creep and oxidation resistance. They are capable of functioning at very high temperatures and severe mechanical stress, and also where high surface stability is required. Solid-solution hardening, work hardening, and precipitation hardening are performed to increase their strength. There are three groups of alloys such as cobalt-based, nickel-based, and iron-based super alloys. All of these can be used at temperatures above 540°C (1000°F).
Hastelloy® N is a nickel base alloy. It is added with molybdenum in order to increase its hot oxidation resistance to fluoride salts.
Chemical Composition
The chemical composition of Hastelloy® N is given in the following table.
|
Element |
Content (%) |
|
Nickel, Ni |
71 |
|
Molybdenum, Mo |
16 |
|
Chromium, Cr |
7 |
|
Iron, Fe |
≤ 5 |
|
Silicon, Si |
≤ 1 |
|
Manganese, Mn |
≤ 0.80 |
|
Tungsten, W |
≤ 0.50 |
|
Aluminum, Al + Titanium, Ti |
≤ 0.50 |
|
Copper, Cu |
≤ 0.35 |
|
Cobalt, Co |
≤ 0.20 |
|
Carbon, C |
≤ 0.080 |
Physical Properties
The physical properties of Hastelloy® N are displayed in the following table.
|
Properties |
Metric |
Imperial |
|
Density |
8.86 g/cm³ |
0.320 lb/in³ |
|
Melting point |
1372°C |
2500°F |
Mechanical Properties
The following table shows the mechanical properties of Hastelloy® N.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
800 MPa |
116000 psi |
|
Elongation at break (in 25.4 mm) |
39.3% |
39.3% |
|
Modulus of elasticity (@14°C) |
219 GPa |
31800 ksi |
Thermal Properties
The thermal properties of Hastelloy® N are outlined in the following table.
|
Properties |
Metric |
Imperial |
|
Thermal expansion co-efficient (@ 21-316°C /69.8-601°F) |
12.3 µm/m°C |
6.83 µin/in°F |
|
Thermal conductivity |
11.5 W/mK |
79.8 BTU in/hr.ft².°F |
Other Designations
Other designations that are equivalent to Hastelloy® N include:
-
AMS 5607
-
AMS 5771
-
ASTM B366
-
ASTM B434
-
ASTM B573
Fabrication and Heat Treatment
Machinability
Hastelloy® N can be machined using conventional machining methods which are used for iron-based alloys. Machining operations are performed using commercial coolants. High-speed operations such as grinding, milling or turning, are performed using water-based coolants. Heavy lubricants are used for, tapping, drilling, boring, or broaching.
Forming
Hastelloy® N is formed using conventional techniques.
Welding
Hastelloy® N is welded using gas-tungsten arc welding, gas metal-arc welding, shielded metal-arc welding. Submerged-arc welding method is not preferred.
Heat Treatment
Hastelloy® N does not respond to heat treatment.
Cold Working
Hastelloy® N can be cold worked using standard tooling. Soft die materials such as zinc alloys, and bronze are used for producing good finish and reducing galling problems. During the sequence of cold forming process, intermediate annealing can be performed.
Annealing
Hastelloy® N is annealed at 1177°C (2150°F) followed by cooling.
Hardening
Hastelloy® N is hardened only by cold working.
Applications
Hastelloy® N is used in chemical process equipments and general industrial applications requiring high temperature oxidation resistance.