DIN EN ISO 4499-4:2016-10

This standard specifies methods for the metallographic determination of the presence, type, and distribution of porosity, uncombined carbon and eta-phase in hardmetals. In standard WC/Co hardmetals, the chemistry and density are generally controlled so that only two phases WC and Co are present. The Co phase is an alloy and contains some W and C in solid solution. The WC phase is stoichiometric. If the composition is either high or low in total carbon content, then it is possible to see a third phase in the structure. For high C, this is graphite; for low C, it is eta phase (η); typically, an M6C or M12C carbide where M is (CoxWy). This standard is concerned with the detection and measurement of these microstructural features together with the measurement of porosity levels. Porosity is important since these materials are manufactured by a powder metallurgical route and although the technique of liquid phase sintering is used to consolidate the multiphase structure, low levels of porosity can arise in some instances and affect properties such as density and strength. This document (EN ISO 4499-3:2016) has been prepared by Technical Committee ISO/TC 119 "Powder metallurgy", Subcommittee SC 4 "Sampling and testing methods for hardmetals". The responsible national standards committee is Working Committee NA 145-01-04 AA "Sampling and testing methods for hardmetals" at DIN Standards Committee Technology of Materials (NWT). The standard differs from DIN ISO 4505:1991-07 as follows: a) the title of the standard has been modified; b) Clause 2 "Normative references", Clause 3 "Terms and definitions", Clause 4 "Symbols and units", Clause 5 "Principle", Subclause 6.2 "Scanning electron microscope", Clause 7 "Calibration of measurement apparatus", Subclause 8.2 "Characterisation of porosity and carbon (graphite) defects" and Subclause 8.3 "Characterisation of eta-phase" have been added; c) Subclause 9.4 "Determination of the η-phase (eta phase) " has been added, including Figure 5 "Large etaphase rosettes (about 100 μm in diameter) " and Figure 6 "Small eta-phase particles (light grey, about 5 μm in diameter) "; d) Clause 10 "Uncertainty of measurement" has been added; e) Test report has been expanded; f) the document has undergone extensive editorial revision.