Element · Mo

Molybdenum

A refractory metal that keeps steel strong when it gets hot.

Molybdenum's industrial role is almost entirely as a steel additive. A small percentage raises the temperature at which a steel loses strength and improves its resistance to pitting corrosion — which is why molybdenum-bearing stainless grades are specified for marine and chemical service.

Its disulfide is also one of the better solid lubricants, working by the same mechanism as graphite: weakly bonded layers that slide over one another.

Uses

Molybdenum is a steel alloying element first. Small additions raise strength at high temperature and resistance to pitting corrosion, which is why pressure vessels, pipelines and high-speed tool steels contain it.

Molybdenum disulfide is a dry lubricant that works where oil would burn off or attract dust, its layered structure shearing easily under load. Molybdenum compounds are also important catalysts in petroleum refining, where they strip sulfur from fuel, and it is an essential trace element in the enzymes that fix nitrogen.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is used as

Alloying — application · raises the temperature at which steel loses strength

is a source for

Rhenium — element · recovered from the flue dusts of molybdenum roasting; rhenium forms no ore of its own

is extracted from

Wulfenite — mineral · a minor ore; molybdenite and copper porphyry roasting supply the rest Wikidata
Molybdenite — mineral · the principal ore, and the flue dusts of roasting it are where rhenium comes from Wikidata

is produced by

Smelting — process · reduced from the oxide that roasting molybdenite produces

is an alternative to

Tungsten — element · in tool and high-speed steels, where molybdenum gives comparable hot hardness at roughly half the density and much of the world's tungsten supply sits in one country

is a component of

Nickel superalloy — alloy · 0–6% · for the same reason as tungsten, at a third the density

is found in

Tool steel — alloy · 0–5% · hardenability and hot strength
High-speed steel — alloy · 0–10% · does the same job as tungsten at roughly half the weight, and most modern grades are molybdenum-based for that reason
Cobalt-chromium alloy — alloy · 5–7% · in the implant alloys, refining the grain and improving strength
Molybdenite — mineral Wikidata
Wulfenite — mineral Wikidata

Sources

Material World
Our own writing
Wikidata
Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
PubChem
US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors
NIST — National Institute of Standards and Technology
United States Department of Commerce · US Government work — public information, credit requested

Questions this page answers

Where it comes from, and what it becomes

Follow Molybdenum back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

Molybdenum → is produced by (reduced from the oxide that roasting molybdenite produces) → Smelting → takes as input (as the element removed, not added) → Oxygen → is produced by (the largest output by tonnage, and the reason air separation units sit beside steelworks) → Air separation → takes as input (the feedstock, and an unusual one in being free, unlimited and available anywhere — the cost is entirely the energy to liquefy it) → Air
Molybdenum → is extracted from (a minor ore; molybdenite and copper porphyry roasting supply the rest) → Wulfenite
Molybdenum → is extracted from (the principal ore, and the flue dusts of roasting it are where rhenium comes from) → Molybdenite
Molybdenum → is produced by (reduced from the oxide that roasting molybdenite produces) → Smelting → takes as input (roasted to drive off sulfur, then reduced to copper) → Chalcopyrite
Molybdenum → is produced by (reduced from the oxide that roasting molybdenite produces) → Smelting → takes as input (reduced with carbon to metallic tin) → Cassiterite
Molybdenum → is produced by (reduced from the oxide that roasting molybdenite produces) → Smelting → takes as input (reduced with coke in a blast furnace) → Hematite

These are the most distinct paths back. Molybdenum can be traced through others besides.

Downstream — what it becomes

Molybdenum → is a source for (recovered from the flue dusts of molybdenum roasting; rhenium forms no ore of its own) → Rhenium → is a component of (two or three per cent, and essentially the only use rhenium has — most of world consumption goes into turbine blades) → Nickel superalloy → is used in (cast as a single crystal, because at temperature and sustained load the failure mode is creep along grain boundaries — so the boundaries are removed entirely) → Turbine blade → is associated with (the jet engine created the superalloy industry, because no existing material survived the turbine inlet — and turbine temperature has risen about 500 °C since, almost entirely on the blade) → The wartime materials programmes complete chain
Molybdenum → is a component of (for the same reason as tungsten, at a third the density) → Nickel superalloy → is used in (cast as a single crystal, because at temperature and sustained load the failure mode is creep along grain boundaries — so the boundaries are removed entirely) → Turbine blade → is associated with (the jet engine created the superalloy industry, because no existing material survived the turbine inlet — and turbine temperature has risen about 500 °C since, almost entirely on the blade) → The wartime materials programmes complete chain
Molybdenum → is used as (raises the temperature at which steel loses strength) → Alloying
Molybdenum → is a component of (for the same reason as tungsten, at a third the density) → Nickel superalloy → is associated with (the jet engine created the industry, because no existing material survived the turbine inlet) → The wartime materials programmes complete chain
Molybdenum → is a source for (recovered from the flue dusts of molybdenum roasting; rhenium forms no ore of its own) → Rhenium → is used in (two or three per cent of the alloy, because it slows diffusion and therefore creep — and blade alloys take most of world rhenium production for it) → Turbine blade → is used in (and the capability is the casting yield and the coating rather than the alloy, whose composition is published — which is why jet engines are a three-company industry) → Aerospace manufacture
Molybdenum → is a source for (recovered from the flue dusts of molybdenum roasting; rhenium forms no ore of its own) → Rhenium → is used as (with platinum, raises the octane rating of petrol) → Catalysis

These are the most distinct paths onward. Molybdenum ends up in others besides.