Metallographic Sample Preparation of Cemented Tungsten Carbides

B665: Standard Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides

Ensuring the integrity and performance of critical components hinges on understanding their internal structure. For professionals working with cemented tungsten carbides, a material prized for its exceptional hardness and wear resistance, accurate microstructure analysis is paramount. ASTM B665 provides the authoritative guidance essential for achieving this precision.

What is B665?

ASTM B665, "Standard Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides," is an industry-leading document established by ASTM International. Its primary purpose is to outline a proven, step-by-step procedure for preparing samples of cemented tungsten carbides for metallographic examination. This standard ensures consistency and reliability in sample preparation, which is fundamental for accurate microstructure analysis.

Scope & Purpose

This comprehensive guide governs the essential processes involved in preparing cemented tungsten carbide samples for metallographic study. It details recommended techniques for mounting, grinding, and polishing to reveal the material's microstructure without causing damage or introducing artifacts. While it provides a robust framework, B665 does not aim to cover every conceivable variation in sample preparation, nor does it address specific safety protocols, which remain the user's responsibility.

Who Must Comply?

• • Primary audience: Materials Engineers, Metallurgists, Quality Inspectors, and Laboratory Technicians involved in the characterization and quality control of cemented tungsten carbides.
• • Industries affected: Aerospace, Automotive, Tooling, Mining, and Industrial Machinery manufacturing sectors where cemented tungsten carbides are integral to component design and performance.
• • Compliance nature: While typically voluntary, adherence to B665 is highly recommended for organizations seeking to ensure the highest levels of accuracy and comparability in their metallographic analyses, particularly for quality assurance and research and development.
• • Enforcement: Compliance is typically self-enforced by organizations to meet internal quality standards or customer specifications. External audits may verify adherence to established procedures.

Key Requirements Overview

The standard requires professionals to select representative sections of cemented tungsten carbide for examination, often utilizing diamond cutting wheels for precise sectioning. Key provisions include the use of diamond abrasives for both grinding and polishing stages, with specific guidance on grit sizes and lapping media. Professionals must ensure meticulous cleaning between each preparation step to prevent contamination and the introduction of artifacts. Furthermore, the guide emphasizes applying adequate pressure during lapping to prevent the pull-out of softer matrix materials, thereby preserving the true microstructure.

Related Standards & References

ASTM B665 works in conjunction with other vital standards. It serves as a foundational preparation guide for ASTM B657, Guide for Metallographic Identification of Microstructure in Cemented Carbides, which details how to interpret the prepared microstructures. While ASTM B390, Practice for Evaluating Apparent Grain Size and Distribution of Cemented Tungsten Carbides, has been withdrawn, the principles of microstructure evaluation it represented are often a driving force behind the need for precise sample preparation as outlined in B665.