Molybdenum is a refractory metal, not a nickel alloy, and it behaves quite differently from everything else in this catalogue. It melts at 2620°C, conducts heat about ten times better than a nickel superalloy, and expands only 5.2 µm/m·°C — less than a third as much as austenitic stainless steel. ASTM B387 and ASTM B386 define six grades: 360 and 361 are unalloyed molybdenum by the vacuum arc-cast and powder metallurgy routes; 365 is the low-carbon arc-cast variant; 363 and 364 are the TZM alloy, molybdenum with titanium, zirconium and carbon, which raises the recrystallisation temperature by some 300°C; and 366 is the molybdenum–30% tungsten alloy specified for molten zinc service. Exotic Alloy manufactures all six as bolts, stud bolts, heavy hex nuts and custom CNC fasteners with full EN 10204 3.1 certification.
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Above roughly 500–600°C in air, molybdenum forms MoO3, which volatilises instead of building a protective scale, so the metal is consumed continuously. Molybdenum fasteners must be used in vacuum, inert gas or a reducing atmosphere, or else protected by a silicide or aluminide coating. In those environments they hold strength far beyond any superalloy. Recrystallised molybdenum is also brittle at room temperature, which is why fasteners are supplied stress relieved rather than fully annealed. If you are unsure whether your duty suits molybdenum, our technical team will confirm before you order.
Molybdenum machines nothing like a nickel alloy. It throws short, broken chips much as cast iron does, it is abrasive, and it barely work-hardens — so tool wear and edge chipping set the limits rather than the gumming and hardening that dominate superalloy practice. It is also notch sensitive, which makes a rolled thread far preferable to a cut one. Exotic Alloy works molybdenum hot, stress relieves rather than fully anneals, and rolls threads wherever the section size allows, so the finished fastener keeps the wrought fibrous grain structure that carries its room-temperature ductility.
The six grades defined by ASTM B387 for bar, rod and wire, and by ASTM B386 for plate and sheet.
| Grade | UNS Designation | Alloy Type & Production Route | Stress Relieved UTS |
|---|---|---|---|
| Molybdenum 360 | R03600 | Unalloyed molybdenum, vacuum arc-cast | 450–620 MPa |
| Molybdenum 361 | – | Unalloyed molybdenum, powder metallurgy | 450–620 MPa |
| Molybdenum 363 | R03630 | TZM, Mo-0.5Ti-0.1Zr, vacuum arc-cast | 585–795 MPa |
| Molybdenum 364 | R03640 | TZM, Mo-0.5Ti-0.1Zr, powder metallurgy | 585–795 MPa |
| Molybdenum 365 | – | Unalloyed molybdenum, low carbon, vacuum arc-cast | 450–620 MPa |
| Molybdenum 366 | – | Molybdenum – 30% tungsten, vacuum arc-cast | 515–655 MPa |
UNS designations are shown where assigned; the ASTM B387 grade number is the primary identifier for this specification.
We are committed to delivering zero-defect molybdenum fasteners. All products undergo rigorous testing including PMI (Positive Material Identification), interstitial analysis for carbon, oxygen and nitrogen against the ASTM B387 limits, dimensional inspection, and material traceability with EN 10204 3.1 certification.
Exotic Alloy exports molybdenum fasteners to vacuum furnace builders, glass plant, semiconductor equipment makers and galvanising operations worldwide. Our dedicated logistics team ensures secure export packaging and timely deliveries by sea and air freight with full customs documentation support.