First, most of the specifications for maraging steels are SAE AMS (Aerospace Material Specification) and not ASTM. ASTM A 579 - 01 covers forgings using maraging steels, and there may be several ASTM F specs that reference them for surgical screws, plates, etc. Try searching for maraging steel at
for more info on ASTM specs. Click on the following link for the relevant SAE AMS specs:
Now, the term maraging comes from Martensite Age Hardening, which describes the process of age hardening a low carbon, iron-nickel lath martensite matrix. One grade of maraging steel (specifically Carpenter's NiMark 250) has the following composition:
C 0.030
Mn 0.10
P 0.010
S 0.010
Si 0.10
Ni 18.0 to 19.0
Mo 4.7 to 5.0
Co 7.0 to 8.0
Ti 0.30 to 0.50
Al 0.050 to 0.15
Ca 0.050
B 0.0030
Zr 0.030
Iron Balance
As you can see, carbon is basically an impurity in this alloy. The age hardening process is similar to that of aluminum alloys: solution heat treating is typically 1 hr at 820 C, then artificial aging for 3-9 hrs at 455-510 C. Using these alloys and heat treatments, an outstanding combination of mechanical properties (strength, elongation, and fracture toughness) can be obtained. For example, a an 18Ni(250) grade, like NiMark 250, can have the following properties:
yield strength = 1700 MPa
tensile strength = 1800 MPa
elongation = 8 %
K1c plane-strain fracture toughness = 120 MPa m^1/2
As a comparison, spring steels that have similar properties would have K1c approximately one order of magnitude less than this. The cost of the alloys are quite high, due to the cobalt content. Cobalt-free alloys have also been developed. You can find more information at