MA750
Ni-15Cr-7Fe-2.5Ti-0.7Al-1.0Nb+Ta (mass%)
Main Features
MA750 is an age-hardening Ni-Cr base alloy that shows, if it receives proper heat treatment, great stress rupture strength and small creep strength even at a high temperature of 816°C and under high stress . In addition, the alloy shows excellent resistance to chemical corrosion and oxidization. When precipitation hardening is performed to MA750 at 704°C, it achieves high strength. If the alloy is used at 593°C or below, higher strength can be realized by coupling cold-work and heat treatment. When using the alloy at 593°C or in higher temperatures, proper quality can be obtained by a three-step heat treatment . However, at 816°C or above , the alloy will lose most of its age-hardening property along with the increase in the temperature. Alloys which had solution treatment or direct aging will maintain their strength up to approximately 982°C.
Examples of applications
Gas turbine rotor blade, wheel, bolt, gas turbine parts, jet engine, ramjet rocket after-burner, pressure container, air roof frame, missile, heat treatment device, testing machine grip, spring material, bellows, honeycomb tray, extrusion dies, etc.
Weldability
Since welding of these types of precipitation hardening alloys is difficult due to problems such as cracking after precipitation, welding must be performed before precipitation hardening. Weld efficiency is 80% or higher, but this efficiency will be cut greatly if various oxides are not removed before welding. Also, since the alloy has brittleness in high temperatures, each layer may require annealing or solution treatment when welding each layer.
Available Product Forms
Various shapes, such as flat-rolled plates, forgings, welding wires, wires, welded pipes and tubes, seamless pipes and tubes can be manufactured.
Specifications
Information on specifications to which MA750 alloy can be ordered.
ASTM UNS N07750
| Bars, Forgings |
|---|
| SB637 |
ASME UNS N07750
| Bars, Forgings |
|---|
| SB-637 |
JIS NCF750
| Plates | Bars |
|---|---|
| G4902 | G4901 |
AMS UNS N07750
| Plates | Bars, Forgings | Pipes and Tubes | Wires |
|---|---|---|---|
| 5542 | 5667 | 5582 | 5698 |
| 5598 | 5668 | 5583 | 5699 |
| 5670 | |||
| 5671 | |||
| 5747 |
Mechanical Properties, Physical Properties
Tensile properties in normal temperature
| Heat treatment conditions | Testing temperature (°C) | Tensile strength (kgf/mm2) |
Yield strength(0.2% offset ) (kgf/mm2) |
Elongation (kgf/mm2) |
|---|---|---|---|---|
| 1149°C×2hr AC | room temperature | 122.0 | 83.0 | 27 |
| 843°C×24hr AC | 538 | 107.0 | 73.8 | 26 |
| 704°C×20hr AC | 649 | 95.6 | 72.4 | 10 |
| 760 | 73.1 | 54.5 | 8 | |
| 871 | 33.1 | 21.2 | 18 | |
| 982 | 10.0 | 6.2 | 31 |
Rupture test value
| Breaking time(hr) | Stress(kgf/mm2) |
|---|---|
| 100 | 34.0 |
| 1000 | 26.6 |
Impact value(kgf•m)
| Normal temperature | 538°C | 816°C |
|---|---|---|
| 5.0 | 6.8 | 9.0 |
Physical Properties
| Specific gravity | Temperature range°C | Specific heat cal/(g•°C) | Coefficient of Thermal expansion 10-6/°C | Electrical resistivity μΩ-cm |
|---|---|---|---|---|
| 8.3 | 1395∼1425 | Normal temperature 0.103 538°C0.136 |
27°C∼93°C 12.1 27°C∼871°C 16.8 |
111 |
Degree of elasticity(kgf/mm2)
| Normal temperature | 538°C | 816°C |
|---|---|---|
| 21.8×103 | 18.8×103 | 16.3×103 |
Specific thermal conductivity(Cal/cm/sec/°C)
| Normal temperature | 538°C | 816°C |
|---|---|---|
| 0.029 | 0.045 | 0.057 |