Jul 9 2013
Topics Covered
Introduction
Chemical Composition
Physical Properties
Other Designations
Fabrication and Heat Treatment
Machinability
Forging
Welding
Annealing
Cold Working
Hardening
Applications
Introduction
Super alloys are widely used in many industries to make components such as gas turbine engines, rocket motors, nuclear reactors, submarines, and petroleum equipment. Super alloys perform very well in high temperature environments.
Super Alloy HPA 255 is also referred to as ferralium alloy 255. HPA stands for high performance alloy. It is an enriched stainless steel of chromium-iron-nickel and has good chemical corrosion resistance and erosion resistance.
The following sections will discuss in detail about super alloy HPA 255.
Chemical Composition
The chemical composition of super alloy HPA 255 is outlined in the following table.
|
Element |
Content (%) |
|
Chromium, Cr |
24 - 27 |
|
Nickel, Ni |
4.5 - 6.5 |
|
Molybdenum, Mo |
2.9 - 3.9 |
|
Copper, Cu |
1.5 - 2.5 |
|
Manganese, Mn |
1.5 max |
|
Silicon, Si |
1 max |
|
Nitrogen, N |
0.1 - 0.25 |
|
Phosphorus, P |
0.04 max |
|
Carbon, C |
0.04 max |
|
Sulfur, S |
0.03 max |
|
Iron, Fe |
Remainder |
Physical Properties
The physical properties of super alloy HPA 255 are tabulated below.
|
Properties |
Metric |
Imperial |
|
Density |
7.8 g/cm3 |
0.282 lb/in3 |
|
Melting point |
1399°C |
2550°F |
Other Designations
Equivalent materials to super alloy HPA 255 are listed below:
-
ASTM A240
-
ASTM A479
-
ASTM A789
-
ASTM A790
-
ASTM A815
Fabrication and Heat Treatment
Machinability
Super alloy HPA 255 can be machined using the common processes, despite the fact that this alloy is comparatively harder to machine than most stainless steels. Slow speeds and heavy, constant feeds will help prevent this alloy from work hardening.
Forging
Forging of super alloy HPA 255 can be performed in the temperature range of 1204-927°C (2200-1700°F). Annealing has to follow this process so as to re-attain optimum corrosion resistance.
Welding
Welding of super alloy HPA 255 can be performed using all the traditional welding methods such as GMAW, GTAW, and SMAW methods. It is recommended that the filler corresponding to the higher alloy material should be selected to provide optimum results.
Annealing
Annealing of this material can be performed at 1037°C (1900°F) and then rapidly cooled.
Cold Working
Cold working can be performed with the use of standard methods. Annealing should follow this process.
Hardening
Super alloy HPA 255 hardens only by cold work; however care should be taken to perform this process in annealed condition for corrosion resistance.
Applications
Super alloy HPA 255 is used in the following application areas:
-
Chemical process equipment used in chlorides or phosphoric acid environments
-
Pumps and valves handling hot slurries.