RAYCHIN LIMITED

Tungsten Fasteners – Comprehensive Product Range

International Standards & Global Designations – Tungsten Fasteners

RAYCHIN LIMITED manufactures tungsten fasteners from vacuum arc melted (VAR) or powder metallurgy processed material conforming to the most widely used national and international specifications. All material is traceable to the mill with complete certifications.

Chemical Composition (Weight %) – Tungsten & Tungsten Alloys

Our tungsten fasteners are produced from vacuum arc melted (VAR) or powder metallurgy processed material conforming to the limits of applicable ASTM and AMS specifications.

Pure Tungsten (ASTM B760)

Tungsten Heavy Alloys (ASTM B777)

Composition per ASTM B777-19 specification.

Metallurgical note: Tungsten is a refractory metal with the highest melting point of all metals (3422°C). It exhibits exceptional high-temperature strength and dimensional stability in vacuum or inert atmospheres. Pure tungsten has high density (19.3 g/cm³) but is difficult to machine due to its brittleness. Tungsten heavy alloys (W-NiFe, W-NiCu) are produced by powder metallurgy, offering improved machinability while maintaining high density (16.85-18.85 g/cm³). The addition of nickel and iron (or copper) creates a matrix that binds tungsten particles, allowing for conventional machining. These alloys are classified by tungsten content (Class 1-4 per ASTM B777) with higher tungsten content providing higher density and strength. Tungsten-rhenium alloys offer improved ductility and low-temperature brittleness. Tungsten-lanthanum oxide (W-La2O3) provides enhanced high-temperature creep resistance and electron emission properties. All tungsten alloys are susceptible to oxidation above 500°C and require protective atmospheres or coatings for high-temperature service in air.

Complete Mechanical & Physical Properties – Tungsten Alloys (MPa / ksi)

Tungsten fasteners are supplied in sintered, annealed, or stress-relieved condition per applicable ASTM specifications. Data represent typical values based on industry standards.

Pure Tungsten – Mechanical Properties (ASTM B760)

Tungsten Heavy Alloys (ASTM B777) – Mechanical Properties

Values per ASTM B777-19 specification. W-NiCu alloys typically have 10-15% lower strength than W-NiFe alloys.

High-Temperature Mechanical Properties – Class 3 (95% W)

High-temperature testing in vacuum or inert atmosphere. Mechanical properties degrade above 800°C due to microstructural changes.

Physical Properties – Tungsten Alloys

High‑Temperature Performance of Tungsten Fasteners

Tungsten is a refractory metal with exceptional high-temperature strength and stability in vacuum or inert atmospheres. It maintains useful mechanical properties up to 3000°C (5432°F) in non-oxidizing environments, making it suitable for extreme temperature applications in rocket engines, plasma facing components, and high-temperature furnaces. Tungsten's melting point of 3422°C (6192°F) is the highest of all metals, and it exhibits the lowest vapor pressure and the highest tensile strength at temperatures above 1650°C. The recrystallization temperature of tungsten is approximately 1200-1400°C, depending on purity and prior cold work. In oxidizing atmospheres, tungsten forms volatile tungsten trioxide (WO₃) above 500°C, leading to rapid oxidation and catastrophic failure. Therefore, tungsten fasteners must be used in vacuum, inert gas, or reducing atmospheres, or protected with oxidation-resistant coatings (such as MoSi₂, SiC, or Ir). Tungsten heavy alloys have lower maximum service temperatures (typically 800-1000°C) due to the presence of lower-melting binder phases (Ni-Fe, Ni-Cu). Tungsten-rhenium alloys offer improved high-temperature strength and ductility, with rhenium additions increasing recrystallization temperature and reducing brittleness.

Elevated Temperature Capabilities

Corrosion Resistance of Tungsten Fasteners

Tungsten has limited corrosion resistance in most environments due to its susceptibility to oxidation and reaction with many chemicals. However, in certain specific conditions, tungsten offers unique advantages.

Oxidation Behavior

Tungsten begins to oxidize rapidly at temperatures above 500°C in air, forming volatile WO₃. This leads to rapid material loss and catastrophic failure. Therefore, tungsten fasteners are not suitable for high-temperature applications in air without protective coatings. Tungsten heavy alloys also suffer from oxidation of the binder phase at elevated temperatures.

Chemical Resistance

Tungsten is resistant to attack by many molten metals and has low solubility in liquid metals such as lithium, sodium, potassium, magnesium, zinc, and silver. This makes it valuable for handling liquid metals in nuclear and metallurgical applications. Tungsten is also resistant to hydrogen up to very high temperatures and is used in hydrogen furnaces. However, it reacts with nitrogen above 1500°C to form nitrides, leading to embrittlement. Tungsten is rapidly attacked by oxidizing acids and hydrogen peroxide.

Manufacturing Standards – Tungsten Fasteners

All tungsten fasteners are manufactured and tested to meet the following standards:

We offer surface finishes: as-sintered, ground, polished, or coated with oxidation-resistant coatings (MoSi₂, SiC, Ir) for high-temperature air service. Controlled sintering and heat treatment processes per ASTM specifications ensure consistent mechanical properties. Specialized CNC grinding and machining for accurate fastener geometry – tungsten alloys require diamond tooling and specialized techniques due to their extreme hardness and brittleness. Class 2A/3A/6g thread fit (where machinable). 100% inspection available including dimensional inspection, density testing, and non-destructive examination. Full traceability and material test reports (MTR) with mill certifications available. AS9100 and ISO 9001:2015 certified quality management. ISO 13485 certified for medical applications with cleanroom packaging available. Build-to-print specials to customer specifications are available.