Nov 19 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesThermal PropertiesOther DesignationsFabrication and Heat Treatment Machinability Forming Welding Forging Cold working Annealing HardeningApplications
Introduction
Super alloys are metallic alloys used at high temperatures above 540ºC (1000ºF) where high surface stability and deformation resistance are mainly required. Three major classes of super alloys include iron-base, nickel-base and cobalt-base alloys. The iron-base super alloys are generally wrought alloys with stainless steel technology. Nickel-base and cobalt-base super alloys may be cast or wrought based on its composition or application. Super alloys are commonly forged, rolled to sheet or produced in various shapes. However, highly alloyed compositions are produced as castings.
The following datasheet provides a detailed description of HASTELLOY(r) G™, which has good resistance to both oxidation and reduction.
Chemical Composition
The following table shows the chemical composition of HASTELLOY(r) G™.
| Element |
Content (%) |
| Chromium, Cr |
21-23.5 |
| Iron, Fe |
18-21 |
| Molybdenum, Mo |
5.5-7.5 |
| Cobalt, Co |
2.5 max |
| Niobium, Nb |
1.75-2.5 |
| Copper, Cu |
1.5 min |
| Manganese, Mn |
1-2 |
| Silicon, Si |
1 max |
| Tungsten, W |
1 max |
| Carbon, C |
0.05 max |
| Phosphorus, P |
0.04 max |
| Sulfur, S |
0.03 max |
| Nickel, Ni |
Remainder |
Physical Properties
The physical properties of HASTELLOY(r) G™ are given in the following table.
| Properties |
Metric |
Imperial |
| Density |
8.91 g/cm³ |
0.322 lb/in³ |
| Melting point |
1343ºC |
2450ºF |
Mechanical Properties
The mechanical properties of HASTELLOY(r) G™ are given in the following table.
| Properties |
Metric |
Imperial |
| Tensile strength |
Min 760 MPa |
Min 110000 psi |
| Yield strength (0.2% offset) |
700-860 MPa |
102000-125000 psi |
| Modulus of elasticity (room temperature) |
192 GPa |
27800 ksi |
| Elongation at break |
Min 20% |
Min 20% |
| Hardness, Brinell ( estimated from Rockwell C for Brinell 10 mm ball/3000 kg load) |
290 |
290 |
| Hardness, Knoop (estimated from Rockwell C) |
345 |
345 |
| Hardness, Rockwell A (estimated from Rockwell C) |
66 |
66 |
| Hardness, Rockwell C |
Max 31 |
Max 31 |
| Hardness, Vickers (estimated from Rockwell C) |
300 |
300 |
Thermal Properties
The thermal properties of HASTELLOY(r) G™ are given in the following table.
| Properties |
Metric |
Imperial |
| Thermal expansion co-efficient (@20ºC/68ºF) |
13 µm/m°C |
7.22 µin/in°F |
Other Designations
Equivalent materials to HASTELLOY(r) G™ are the following:
- ASTM B581
- ASTM B582
- ASTM B619
- ASTM B622
- ASTM B626
- DIN 2.4618
Fabrication and Heat Treatment
Machinability
HASTELLOY(r) G™ can be machined using conventional techniques employed for iron based alloys. The quality of the alloy can be improved with the utilization of water-base coolants. Heavy duty machining tools and equipment can be used prior to cutting in order to reduce chattering or work-hardening of the alloy.
Forming
HASTELLOY(r) G™ can be formed through conventional forming methods.
Welding
Welding of HASTELLOY(r) G™ is performed through commonly used welding techniques like gas tungsten arc welding, shielded metal-arc welding, metal-arc welding and submerged-arc welding. However, an alloy filler metal that suits this alloy should be used.
Forging
HASTELLOY(r) G™ can be forged at 927 to 1149ºC (1700 to 2100ºF).
Cold working
HASTELLOY(r) G™ can be cold worked using standard tooling methods. As plain carbon steels has an ability to produce galling, they are not preferred for forming HASTELLOY(r) G™. Galling can be minimized with the help of heavy duty lubricants.
Annealing
Annealing of HASTELLOY(r) G™ can be performed at 1177ºC (2150ºF) followed by rapid cooling of air and water quenching.
Hardening
HASTELLOY(r) G™ can be hardened by cold working.
Applications
HASTELLOY(r) G™ finds its application in wet flue gas desulfurization process and manufacture of chemical process equipment.