Jul 24 2013
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.