Description

Udimet ® alloy 250

ultra-high strength, toughness and resistance to crack propagation. The alloy is well suited to applications where heat treatment distortion and dimensional changes must be minimized and where high fracture toughness is required, such as rocket motor casings, light aircraft landing gear, power shafts and low temperature tooling.

The 18% nickel maraging steels offer a unique combination of properties not available from conventional low alloy ultra-high strength steels. They offer high strength, high ductility and toughness, and resistance to crack propagation. Hardening is accomplished by a simple aging cycle of 3 hours at 900°F (482°C) followed by air cooling.

250 provides through hardening without quenching, freedom from decarburization, minimal distortion during aging, good formability, machinability, and weldability and a low coefficient of thermal expansion.

 

 

Available Products and Specifications

Udimet alloy 250 is designated UNS K92890 and UNS K92940. The alloy is available as forging billet and bar.

 

Typical Mechanical Properties

Table 3 – Typical Mechanical Properties of Udimet alloy 250

Carbon………………………………………………………….. 0.03 max.

Silicon…………………………………………………………… 0.10 max.

Manganese……………………………………………………. 0.10 max.

Sulfur…………………………………………………………… 0.010 max.

Phosphorus…………………………………………………. 0.010 max.

Cobalt……………………………………………………………….. 7.0-8.5

Nickel……………………………………………………………. 17.0-19.0

Molybdenum………………………………………………………. 4.6-5.1

Titanium…………………………………………………………. 0.30-0.50

Aluminum……………………………………………………….. 0.05-0.15

Iron………………………………………………………………… Balance*

 

*Reference to the ‘balance’ of a composition does not guarantee this is exclusively of the element mentioned but that it predominates and others are present only in minimal quantities.

 

 

Physical Constants

Table 2 – Physical Constants

Density, lb/in³……………………………………………………….. 0.290

g/cm³…………………………………………………………… 8.0

Melting Range, °F………………………………………….. 2600-2650

°C………………………………………….. 1427-1454

Specific Heat, Btu/lb•°F………………………………………….. 0.07

J/kg•°K……………………………………………… 293

Permeability at 200 Oersted (15.9 kA/m)…………………….. 77.5

Coefficient of Expansion, 70-200°F, 10^-6 in/in•°F…………… 5.4

21-93°C, µm/m•°C………………. 9.72

Thermal Conductivity, Btu•in/ft²•h•°F…………………………. 136

W/m•°C…………………………………. 19.6

Electrical Resistivity, ohm•circ•mil/ft…………………………. 294.4

micro-ohm•cm………………………… 48.9

Young’s Dynamic Modulus, ksi…………………………. 26.4 x 10³

GPa…………………………………….. 182.0

 

	Solution Annealed 1500°F (816°C), 1 hr, AC	Solution Annealed Plus Aged 900°F (482°C), 3 hrs, AC
0.2% Yield Strength, ksi	115	260
Ultimate Tensile Strength, ksi	145	270
Elongation, %	20	10
Reduction of Area, %	70	60
Hardness, Rc	30	50