CCM Vickers Key Comparison - State of the art and perspectives

In the framework of the Working Group on Hardness (WGH) of the Consultative Committee for Mechanical Measurements (CCM) in the year 2003 the key comparison Vickers was finished. In the comparison the hardness laboratories of 10 national metrology institutes participated: IMGC (Italy), NIST (USA), INMETRO (Brazil), NIM (P.R. China), KRISS (Republic of Korea), NMIJ (Japan), CMI (Czech Republic), GUM (Poland), NPL (U.K.), and PTB (Germany) served as the pilot laboratory. The comparison of the Vickers primary hardness standard machines was carried out with three sets of hardness reference blocks of the Vickers scales HV0,2, HV1 and HV 30 each with the hardness levels 240 HV, 540 HV and 840 HV. The Vickers key comparison for all used test forces ranges (Micro Vickers, Small Force Vickers, Macro Vickers) delivered valuable metrological data, and its main results are presented. The ways to determine the reference values are discussed. The uncertainties of the reference values can be considered as the present accuracy limits of Vickers measurements in the investigated ranges of hardness scales