Type Analysis | Description | Physical Properties | Heat Treatment
Workability | Typical Mechanical Properties

Type Analysis

Description

Maraging alloy 300 is a vacuum induction melted plus vacuum arc remelted, low-carbon, nickel-cobalt-molybdenum high temperature alloy capable of attaining yield strengths in excess of 270 ksi (1862 MPa) through simple, low temperature heat treatment at 900°F (482°C). This alloy exhibits good ductility a high strength levels, excellent notch ductility, and is readily welded. Mar300 is one of a family of "maraging" nickel steels which is martensitic yet ductile in the solution treated condition and attains ultrahigh strength through a single low temperature aging treatment.

Physical Properties

Specific gravity .............................. 8.00                                Electrical resistivity
Density                                                                                          ohms c/mf (70°F)........................... 232
  lb/cu in ........................................ 0.289                                    microhm-mm (21.1°C) ................... 390
  kg/cu m ........................................ 8000                               Mean coefficient of thermal expansion
                                                                                                       10(-6)/°F (75/900°F)...................... 5.6
                                                                                                       10(-6)/°C (23.9/482°C)................ 10.1

Heat Treatment

Annealing and Solution Treating
Annealing and solution treating are performed simultaneously by heating to 1500°F +/-50°F for a minimum of 30 minutes at temperature, followed by air cooling to room temperature. A minimum heating rate of 8°F/minute is suggested to prevent overaging and austenite reversion during heating. Course grain structures can be refined by thermal cycling between room temperature and 1500/1700°F.

Aging
Full properties are developed by an aging treatment of 850/900°F for 9 to 4 hours respectively. Usually the alloy is aged at 900°F for a minimum of 3 hours to a maximum of 6 hours, followed by air cooling. Shrinkage on aging is .001in/in.

Workability

Hot working
Hot working is performed by conventional methods over a broad temperature range extending up to 2300°F. Temperatures below 2150°F are recommended to preserve grain structure and prevent severe oxidation. It is suggested, that finishing temperatures be close to 1700°F for Mar300 in order to obtain best properties.

Cold working
Despite the martensitic structure of this alloy and high Rockwell C hardness (approx. 32) in the annealed condition, Mar300 is readily cold worked. Its work-hardening rate is low, as demonstrated by the fact that it can be cold rolled as much as 80% between anneals. Direct aging after cold working will enhance strength while reducing toughness and ductility.

Machinability
Mar300 is readily machined in the solution treated (annealed) condition. Limited machining can be performed in the fully treated condition. Annealed hardness is typically 32 Rc.

Welding
Mar300 can be welded using conventional welding methods and electrodes of approximately the same composition as the base material. Pre-heating is not required. A postweld aging of 850/900°F is required to attain optimum properties in the weld and the heat-afftected zone.

Typical Mechanical Properties

Typical Room Temperature Mechanical Properties
Bars under 4" diameter, treated 1500°F 30 min., air cooled and aged 900°F 3 hours, air cooled.

Notched Tensile Strength to Unnotched Tensile Strength....................>1
Fatigue Life - endurance limit
ksi.........................................................................................................125
Mpa.......................................................................................................862
Fracture Toughness (approx.)
ksiûin. ...................................................................................................70
Transverse Strength..............similar to longitudinal values while ductility is typically 80% of longitudinal values

Typical Elevated Temperature Tensile Strength

Maraging 300 - Current Inventory Stock