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INTERCOMPARISON OF MICRO-HARDNESS MEASUREMENTS

Objective



Hardness measurements are a comparatively quick and simple method of checking upon the quality of a material since the resistance to indentation is related to strength. As a result a number of hardness scales have been developed based upon the dimensions of the indentations made when diamonds or balls are pressed into the material under known loads.

For small components, thin coatings, brittle materials or where the part may not be destroyed and the presence of a macro-indentation would be deleterious, so called micro-hardness techniques are applied upon the same principles but using much smaller indenters and loads (200 g). The purpose of the project was to determine the level of agreement on Vickers - micro - hardness measurements between the laboratories of the Community Member States and to examine the metrological problems.

RESULTS

The project was terminated 1990.

Steel, copper and brass micro-hardness blocks were circulated to the participating laboratories. Measurements made by the pilot laboratory at the beginning and the end of the intercomparison showed that the hardnesses of the blocks were stable with time.
The laboratories were requested to measure the diagonals of a series of indentations made by the pilot laboratory under undisclosed conditions and to make their own hardness determinations under specified conditions.
The measurements of four laboratories of the lengths of identical indentations were in good agreement (discrepancies of the order of tenths of a micron) whilst one laboratory showed a systematic discrepancy over the whole range of lengths. The reason maybe that the line standard was not properly applied or the zero adjustment was faulty.
One of the four laboratories made its own indentations using a sputtered indenter which had significant influence on its results. The remaining three laboratories were in good agreement (deviations in general less than 2%.HV).

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

TECHNISCHE UNIVERSITAET BERLIN
Address
Marchstraße 12-14
10587 Berlin
Germany

Participants (4)

Dantest
Denmark
FEDERAL INSTITUTE FOR MATERIAL RESEARCH AND TESTING
Germany
Address
87,Unter Der Eichen 87
12205 Berlin
Imgc
Italy
MPA NRW
Germany