engleski

Metrological characteristics of newly developed reference Vickers hardness block for the high hardness range

The paper describes the development and characterisation of metrological characteristics of reference Vickers hardness blocks for high hardness range, development of the system for the indentation analysis and interlaboratory comparison. The primary goal of the research was to develop the reference Vickers hardness block from nanostructured hardmetal with the hardness value of approximately 2000 HV1. Based on the long-lasting and extensive research the reference Vickers hardness blocks with optimal metrological characteristics were selected and presented in the paper. Two blocks consolidated by different powder metallurgy processes ; sintering in a hydrogen atmosphere and sinter- HIP process were described. The surface of the blocks was researched in terms of material and metrological characteristics and prepared to maintain the requirements according to EN ISO 6507-3:2005, concerning flatness, parallelism and surface roughness. In order to achieve more accurate and precise measurements of indentations, the lengths of diagonals were measured in the 1D optical measurement system (1D OMS) developed by the National Laboratory for Length HMI/FSB-LPMD for high accuracy line scale calibration. The custom software was developed in Visual Studio 2012. In order to confirm the reliability of the hardness values determined on 1D OMS and newly developed software for indentation analysis, the interlaboratory comparison was performed on the primary micro-hardness machine installed in the Physikalische-Technische Bundesanstalt PTB, Germany. From the conducted research it was concluded that preliminary Vickers hardness blocks were developed successfully from nanostructured hardmetals. Higher hardness and lower non-uniformities over the test surface were achieved for fully dense block consolidated by a sinter-HIP process. The intercomparison confirmed the reliability of the measured results determined on the reference hardness standard and 1D OMS with newly developed software.

nanostructured hardmetal, Vickers hardness block, high hardness range, metrological characteristics, optical measurement system and software for indentation analysis, laboratory intercomparisons

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