Die zulässige Spannung von zementiertem Wolframkarbid

Cemented tungsten carbide is frequently used in engineering design, and understanding allowable stress of cemented tungsten carbide helps engineers select suitable materials. Allowable stress refers to the maximum stress a material can safely withstand long-term; exceeding this value may cause deformation or fracture. As a representative hard alloy, the allowable stress of cemented tungsten carbide is influenced by composition, temperature, processing techniques, and other factors. Specific values require analysis based on actual conditions.

Composed of tungsten and carbon atoms, cemented tungsten carbide approaches the hardness of natural diamond and exhibits exceptional wear resistance. This material often uses cobalt as a binder phase—higher cobalt content improves toughness but may reduce hardness and allowable stress. For instance, cemented tungsten carbide with 6% cobalt typically has a compressive strength between 4,000–5,000 MPa, though the practical allowable stress applies a safety factor, typically 1/5 to 1/3 of the compressive strength.

Temperature significantly impacts allowable stress. While stable at room temperature, cemented tungsten carbide softens above 500°C, causing allowable stress to drop sharply. Experimental data show that allowable stress decreases by approximately 8%–12% per 100°C temperature increase. High-temperature applications require careful attention to cooling system design and temperature monitoring.

Manufacturing processes directly determine material performance. cemented tungsten carbide produced via low-pressure sintering reduces porosity by 0.5%–1% compared to conventional methods, increasing allowable stress by over 15%. Surface treatments like chemical vapor deposition (CVD) coatings form a 5–10 μm titanium nitride layer, boosting surface allowable stress by about 20% without compromising bulk toughness.

Stress concentration must be addressed in practical applications. Due to its brittleness, sharp edges should be avoided in part design. One tool manufacturer reported that increasing the cutting edge radius from 0.1 mm to 0.3 mm extended tool life threefold. Preload control during assembly is also critical, as excessive stress may initiate microcracks.

Allowable stress values vary across standards. ASTM B657 specifies an allowable stress range of 800–1,200 MPa for industrial-grade cemented tungsten carbide, while DIN 4990 provides 600–1,000 MPa for specific conditions. Selection should consider the application scenario—e.g., lower values for impact loads and mid-to-upper values for static loads.

Maintenance affects the durability of allowable stress. Regular inspection for surface wear is essential; spalling exceeding 0.2 mm may reduce load-bearing capacity by 30%. Lubricant selection also matters: grease with solid lubricants can reduce contact stress by 15%–20% compared to standard oils.

Material inspection is crucial for ensuring allowable stress. Ultrasonic testing detects internal defects as small as 0.1 mm, and X-ray diffraction analyzes residual stress distribution. Destructive testing—including three-point bending and compression tests—should be performed per batch to verify compliance with design requirements.

An engineering case study shows that replacing a gear shaft in mining machinery with cemented tungsten carbide increased the allowable stress by 50% compared to the original design, though this required improved support structures. This modification extended equipment lifespan from 6 months to 3 years, demonstrating the significant benefits of properly applying allowable stress data. Note that material parameters should never be applied blindly; comprehensive analysis tailored to specific operating conditions is essential.