STP889

    Fabrication and Certification of Electroformed Microhardness Standards

    Published: Jan 1985


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    Abstract

    A commonly quoted characteristic of a material is its hardness. Accurate measurements of this characteristic require the use of precise standards to verify that the testing instrument, procedures, and comparisons with the results of another laboratory are accurate; however, it is recognized that currently available standards vary considerably in hardness from point to point across the surface. Electroplating technology was utilized to fabricate new microhardness standards. This technology provides a means for obtaining uniform hardness by close control of process variables which determine grain structure and composition.

    Two microhardness standards are now in production—one with a hardness of ∼125 kg/mm2 and the other at ∼600 kg/mm2. The hardness values are certified at loads of 0.245, 0.490, and 0.981 N (25, 50, and 100 gf) with both Vickers and Knoop indenters. These electroplated materials have standard deviations in hardness, particularly at low loads, that are significantly better than the available standards. The fabrication of the new standards, their certification procedures, and testing instrument characteristics are discussed.

    Keywords:

    hardness, Knoop hardness, Vickers hardness, hardness testing metrology, nondestructive testing, testing instruments, microindentation hardness testing


    Author Information:

    Kelley, DR
    Physical science technician, physical scientist, and group leader and metallurgist, Center for Materials Science, National Bureau of Standards, Washington, DC

    Johnson, CE
    Physical science technician, physical scientist, and group leader and metallurgist, Center for Materials Science, National Bureau of Standards, Washington, DC

    Lashmore, DS
    Physical science technician, physical scientist, and group leader and metallurgist, Center for Materials Science, National Bureau of Standards, Washington, DC


    Paper ID: STP32958S

    Committee/Subcommittee: E04.05

    DOI: 10.1520/STP32958S


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