Jul 24 2013
Topics Covered
Introduction
Chemical Composition
Physical Properties
Other Designations
Fabrication and Heat Treatment
Machinability
Forming
Welding
Heat Treatment
Forging
Cold Working
Applications
Introduction
Super alloys exhibit excellent mechanical strength and creep resistance at elevated temperatures, good surface stability, and good corrosion and oxidation resistance.
Super alloy Nicrofer 4823 hMo is a modified version of Hastelloy G with higher molybdenum and tungsten contents to enhance this alloy’s corrosion resistance to welded heat-affected zone.
The following sections will discuss in detail about super alloy Nicrofer 4823 hMo.
Chemical Composition
The chemical composition of Nicrofer 4823 hMo is outlined in the following table.
|
Element |
Content (%) |
|
Chromium, Cr |
21 - 23.5 |
|
Iron, Fe |
18 - 21 |
|
Molybdenum, Mo |
6-8 |
|
Cobalt, Co |
5 max |
|
Copper, Cu |
1.5 - 2.5 |
|
Tungsten, W |
1.5 max |
|
Silicon, Si |
1 max |
|
Manganese, Mn |
1 max |
|
Niobium (Nb) +Tantalum (Ta) |
0.5 max |
|
Phosphorus, P |
0.04 max |
|
Sulfur, S |
0.03 max |
|
Carbon, C |
0.015 max |
|
Nickel, Ni |
Remainder |
Physical Properties
The physical properties of Nicrofer 4823 hMo are tabulated below.
|
Properties |
Metric |
Imperial |
|
Density |
g/cm3 |
0.3 lb/in3 |
|
Melting point |
1343°C |
2450°F |
Other Designations
Equivalent materials to Nicrofer 4823 hMo are listed below:
-
ASTM B581
-
ASTM B582
-
ASTM B619
-
ASTM B622
-
ASTM B626
-
DIN 2.4619
Fabrication and Heat Treatment
Machinability
Super alloy Nicrofer 4823 hMo 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.
Water-based coolants of high quality are recommended for use. Carbide tools and high-speed tools can be used for the machining operations.
Forming
Super alloy Nicrofer 4823 hMo can be cold formed using conventional methods.
Welding
Welding of super alloy Nicrofer 4823 hMo can be performed using traditional welding methods. Matching alloy filler metal is required. Preheating and/or post heating are not required. The weld beads should be slightly convex. Slag has to be completely removed after every operation. Surfaces to be welded should be clean and free from oil, paint or crayon marking.
Heat Treatment
Super alloy Nicrofer 4823 hMo can be annealed but not age hardened. Annealing should be performed after hot or cold working so as to re-attain optimum corrosion resistance. Anneal at 1149°C (2100°F) and rapidly air cool or water quench.
Forging
Forging can be performed in the temperature range of 1149 to 927°C (2100 to 1700°F). It is recommended that annealing be done after forging to re-attain corrosion resistance.
Cold Working
Nicrofer 4823 hMo can be easily cold worked.
Applications
Nicrofer 4823 hMo is chiefly used in process equipment for sulfate compounds, mixed acids, and flue gas scrubbers.