Overview
SIST EN ISO 3908:2009 outlines a standardized gravimetric method for the precise determination of insoluble (free) carbon content in hardmetals and carbides. Developed by the International Organization for Standardization (ISO) under technical committee ISO/TC 119 "Powder metallurgy," this method replaces the earlier EN 23908:1993 standard. It is applicable across a range of carbides and their mixtures with binder metals, essential in the manufacturing and quality control of presintered or sintered hardmetals.
The standard is relevant for carbides of hafnium, molybdenum, niobium, tantalum, titanium, vanadium, tungsten, and zirconium and their binder metal mixtures, specifically for insoluble carbon mass fractions ranging between 0.02% and 0.5%. The gravimetric approach ensures reliable quantification of free carbon, which is critical in determining the physical and chemical properties of hardmetals used in industrial applications.
Key Topics
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Scope of Application
Applicable to carbides and hardmetals free of lubricants, including both presintered and sintered grades.
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Principle
Decomposition of the hardmetal sample to isolate insoluble carbon, followed by gravimetric measurement through combustion and carbon dioxide quantification.
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Reagents and Safety
Use of nitric acid (ρ=1.20 g/ml) and hydrofluoric acid (ρ=1.12 g/ml) for sample dissolution. Strict safety protocols must be followed due to the hazardous nature of hydrofluoric acid.
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Analytical Apparatus
Involves specialized equipment such as a platinum dish, ceramic or refractory fibrous filter devices (Gooch crucible), and vacuum filtration assembly.
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Procedure Summary
Crushing and sieving of samples, acid digestion on a steam bath, vacuum filtration to collect insoluble carbon particles, followed by combustion in an oxygen stream at ~1200 °C.
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Calculation and Results
Calculation of mass fraction of insoluble carbon using the mass of carbon dioxide released, with defined tolerances ensuring precision across multiple determinations.
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Test Reporting Requirements
Comprehensive documentation including reference to this standard, sample details, results, deviations, and any procedural anomalies.
Applications
SIST EN ISO 3908:2009 is integral for manufacturers and quality control laboratories involved in:
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Hardmetal Production
Ensuring correct free carbon content to optimize mechanical strength, wear resistance, and other critical properties in cutting tools, mining equipment, and wear parts.
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Powder Metallurgy Industry
Validating raw material suitability and finished product conformity for high-performance alloys and composite materials.
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Materials Research
Analyzing carbides and their composites for development of new grades of hardmetals with tailored physical and chemical characteristics.
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Regulatory Compliance
Fulfilling European and international quality standards for hardmetal products.
Related Standards
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ISO 3907:2009 - Specifies a gravimetric method for the determination of total carbon in hardmetals, which complements the free carbon analysis defined in ISO 3908.
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EN 23908:1993 - The superseded version of this standard, replaced by SIST EN ISO 3908:2009 for updated methodology and requirements.
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ISO/IEC Directives, Part 2 - Governs the drafting and approval process for International Standards, ensuring consistency across procedures such as those described in SIST EN ISO 3908:2009.
Keywords: SIST EN ISO 3908:2009, free carbon determination, gravimetric method, hardmetals, carbides, powder metallurgy, insoluble carbon, metallurgical analysis, quality control, sintered hardmetals, carbide analysis.