RAYCHIN LIMITED

Molybdenum Socket Head Cap Screws – Design & Configurations

Critical Applications of Molybdenum Socket Head Cap Screws

International Standards & Global Designations – Molybdenum Socket Head Cap Screws

RAYCHIN LIMITED manufactures molybdenum socket head cap screws from vacuum arc melted (VAR) or powder metallurgy (PM) material conforming to the most widely used national and international specifications. All material is traceable to the mill.

Chemical Composition (Weight %) – Molybdenum Alloys for Socket Head Cap Screws

Our molybdenum socket head cap screws are produced from vacuum arc melted (VAR) or powder metallurgy (PM) material conforming to ASTM B386/B387 and industry standards.

Pure Molybdenum (Grade 360 / 361) – Mo ≥99.95%

TZM Alloy (Grade 363 / 364) – Mo-0.5Ti-0.08Zr-0.02C

MoLa Alloy (Mo with Lanthanum Oxide)

Metallurgical note: Molybdenum is a refractory metal with a body-centered cubic (BCC) crystal structure. Pure molybdenum socket head cap screws are typically supplied in stress-relieved condition (recrystallization temperature ~1100°C). TZM alloy offers significantly higher recrystallization temperature (~1400°C) and improved creep strength through carbide dispersion strengthening. MoLa (lanthanated molybdenum) maintains ductility after high-temperature exposure due to oxide dispersion pinning grain boundaries. All molybdenum socket head cap screws should be handled with care due to limited ductility at room temperature, becoming more ductile above ductile-to-brittle transition temperature (DBTT).

Complete Mechanical & Physical Properties – Molybdenum Socket Head Cap Screws (MPa / ksi)

Molybdenum socket head cap screws are supplied in various conditions (hard/stress relieved, soft/annealed) per ASTM B387. Data represent typical values based on industry standards and are compared with SUS304 stainless steel for reference.

Mechanical Properties – Pure Molybdenum vs. SUS304

Mechanical Properties – TZM Alloy Socket Head Cap Screws

Physical Properties – Pure Molybdenum vs. SUS304

High‑Temperature Performance of Molybdenum Socket Head Cap Screws

Molybdenum and its alloys are renowned for exceptional high-temperature strength and stability. Pure molybdenum maintains useful mechanical properties up to 1700°C (3090°F) in vacuum or reducing atmospheres, with TZM extending capability further through carbide strengthening. Molybdenum has a melting point of 2623°C (4743°F), making it ideal for the highest temperature environments. However, molybdenum oxidizes rapidly above 600°C in air, forming volatile MoO₃, limiting use to vacuum, inert gas, or reducing atmospheres unless protected by coatings.

Elevated Temperature Capabilities

Molybdenum socket head cap screws support use with vacuum equipment in high-temperature environments. The ventilation hole option (SVSM series) provides complete degassing for UHV applications. In oxidizing atmospheres above 600°C, sublimation will occur; use is therefore recommended only in vacuum, inert gas, or reducing atmospheres. For air applications, protective coatings (MoSi₂, Al₂O₃, Y₂O₃) may be applied.

Corrosion Resistance of Molybdenum Socket Head Cap Screws

Molybdenum exhibits excellent resistance to many corrosive media, particularly in reducing environments and in the absence of oxidizing agents. However, rapid oxidation occurs in air above 600°C. Its stability in various chemical environments makes it suitable for chemical processing equipment and research applications.

• Oxidation Resistance: Forms volatile MoO₃ above 490-600°C in air; requires protective atmosphere or coating for high-temperature air service. Sublimation begins at 600°C in oxidizing atmosphere.
• Acid Resistance: Excellent resistance to hydrochloric acid (HCl) at moderate temperatures. High solubility in concentrated sulphuric acid and nitric acid. Resists most non-oxidizing mineral acids.
• Halogen Resistance: Resistant to fluorine, chlorine, and bromine at moderate temperatures.
• Liquid Metals: Excellent resistance to liquid lithium, sodium, potassium, and bismuth, making it valuable in nuclear coolant systems. Resists molten aluminum and zinc.
• Hydrogen: Excellent resistance to hydrogen attack even at high temperatures.
• Glass Corrosion: Outstanding resistance to molten glass, widely used in glass melting electrodes and stirrers.
• Chloride Solutions: Molybdenum-containing alloys have superior resistance against pitting attack in chloride solutions.
• Environmental Stability: Molybdenum occurs naturally in fresh water and sea water as MoO₄²⁻ in oxidised environments.

Manufacturing Standards – Molybdenum Socket Head Cap Screws

All molybdenum socket head cap screws are manufactured and tested to meet the following standards:

We offer surface finishes: black (as-machined), chemical cleaned, ground, polished, and passivated. Special coatings (MoSi₂, Al₂O₃, Y₂O₃) available for oxidation protection. Cleanroom wash and cleanroom packaging available for semiconductor, medical, and aerospace applications – batch cleanroom packing provided for orders containing multiple items of the same size. Full traceability and destructive/non‑destructive testing available (UT, PMI, MPI). ISO 9001, AS9100D, ISO 13485 certified.