RAYCHIN LIMITED

Molybdenum Washers – Design & Configurations

Critical Applications of Molybdenum Washers

International Standards & Global Designations – Molybdenum Washers

RAYCHIN LIMITED manufactures molybdenum washers 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 Washers

Our molybdenum washers 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 washers are typically supplied in stress-relieved condition (recrystallization temperature ~1100°C) or soft/annealed condition. 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 washers 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 Washers (MPa / ksi)

Molybdenum washers are supplied in various conditions (hard/stress relieved, soft/annealed) per ASTM B387. Data represent typical values based on industry standards.

Mechanical Properties – Pure Molybdenum Washers

Mechanical Properties – TZM Alloy Washers

Physical Properties – Molybdenum (vs Stainless Steel SUS304)

High‑Temperature Performance of Molybdenum Washers

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. However, molybdenum oxidizes rapidly above 600°C in air, forming volatile MoO₃, limiting use to vacuum, inert gas, or reducing environments unless protected by coatings.

Elevated Temperature Capabilities

High-Temperature Comparison – Molybdenum vs. Stainless Steel

Note: All molybdenum washers must be used in vacuum, inert gas, or reducing atmosphere (H₂) above 600°C to prevent catastrophic oxidation. For air applications, protective coatings (MoSi₂, Al₂O₃, Y₂O₃) may be applied.

Corrosion Resistance of Molybdenum Washers

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.

• Acid Resistance: Excellent resistance to hydrochloric acid (HCl), sulfuric acid (H₂SO₄) up to 60% concentration at moderate temperatures, and phosphoric acid (H₃PO₄). Resists most non-oxidizing mineral acids. Rapid attack in nitric acid (HNO₃) and other oxidizing acids.
• Alkalis: Stable in alkaline solutions (sodium hydroxide, ammonia), resisting corrosion effectively.
• Liquid Metals: Excellent resistance to liquid lithium, sodium, potassium, and bismuth, making it valuable in nuclear coolant systems. Resists molten aluminum and zinc.
• Halogens: Resistant to fluorine, chlorine, and bromine at moderate temperatures; forms halides at higher temperatures.
• Oxidation: Forms volatile MoO₃ above 600°C in air; requires protective atmosphere or coating for high-temperature air service.
• Hydrogen: Excellent resistance to hydrogen attack even at high temperatures (unlike steel).
• Sulfur Compounds: Good resistance to sulfur, hydrogen sulfide, and sulfur dioxide.
• Glass Corrosion: Outstanding resistance to molten glass, widely used in glass melting electrodes and stirrers.
• Halide Salts: Resistant to corrosion and pitting attack by chlorides.
• Electrochemical Corrosion: Excellent resistance to electrochemical corrosion and oxidation.
• Bimetallic Corrosion: Can be safely connected to tungsten, tantalum, and graphite. Avoid direct contact with aluminum, zinc, and copper at high temperatures due to eutectic formation.
• Neutron Irradiation: Excellent resistance to radiation damage, retaining mechanical properties under neutron flux.

Manufacturing Standards – Molybdenum Washers

All molybdenum washers 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. Full traceability and destructive/non‑destructive testing available (UT, PMI, MPI). ISO 13485 certified for medical applications with cleanroom packaging available. Batch cleanroom packaging available for orders containing multiple items of the same size.