Molybdenum uses

Maraging Steels

Maraging steels are carbon free iron-nickel alloys with additions of cobalt, molybdenum, titanium and aluminium. The term maraging is derived from the strengthening mechanism, which is transforming the alloy to martensite with subsequent age hardening.

Table 1 summarizes the alloy content of the 18% nickel – cobalt - molybdenum family as developed by Inco in the late 1950s.

Air cooling the alloy to room temperature from 820°C creates a soft iron nickel martensite, which contains molybdenum and cobalt in supersaturated solid solution. Tempering at 480 to 500°C results in strong hardening due to the precipitation of a number of intermetallic phases, including, nickel-molybdenum, iron-molybdenum and iron-nickel varieties.

Maraging Steels
Type	Yield Strength (0,2% proof stress) (MPa)	% Alloy content
Type	Yield Strength (0,2% proof stress) (MPa)	Ni	Co	Mo	Ti	Al
18Ni1400	1400	18	8.5	3	0.2	0.1
18Ni1700	1700	18	8	5	0.4	0.1
18Ni1900	1900	18	9	5	0.6	0.1
18Ni2400	2400	17.5	12.5	3.75	1.8	0.15
17Ni1600 (cast)	1600	17	10	4.6	0.3	0.05

Table 1: Summary of the alloy content of the 18% nickel – cobalt - molybdenum family

With yield strength between 1400 and 2400 MPa maraging steels belong to the category of ultra-high-strength materials. The high strength is combined with excellent toughness properties and weldability.

Long products for the aircraft industry (Courtesy of Boehler AG, Austria)

Typical applications areas include:

aerospace, e.g. undercarriage parts and wing fittings,
tooling & machinery , e.g. extrusion press rams and mandrels in tube production, gears
Ordnance components and fasteners.

A comprehensive summary on maraging steels is available from the Nickel Institute website (Publication No 4419)