Particularly in the case of micro hardness testing, the parts to be tested are often embedded.
Material specimens are embedded in resin to make it easier to handle them until the optimum preparation result has been achieved. Heat-treated and surface-coated specimens should always be embedded.
Note: The best results are achieved when specimens are carefully cleaned before embedding. The specimen surface must always be free of grease, so that the resin adheres optimally to the specimen material. All other contamination must also be removed.
Various resins and two embedding processes are available for the different purposes and tasks: hot embedding and cold embedding.
Selection of the correct embedding process
Depending on the number of specimens and the required preparation quality, both embedding processes (hot/cold) have various benefits.
Hot embedding is the ideal choice when numerous specimens need to be prepared successively. The embedding results are always of a high quality with a uniform size and shape, and the processing time is relatively short.
Cold embedding is suitable for large quantities of specimens that need to be embedded simultaneously. This process is also suitable for single specimens. Hot-embedding materials are generally cheaper than cold-embedding materials. However, this process necessitates acquisition of a hot-embedding press.
Once the specimens have been embedded, use of special specimen holders is recommended for hardness testing. They guarantee plane parallelism and consequently the correct angle between test part and indenter.
Tipping and slipping are also prevented.
A further aspect regarding use of specimen holders is the testing height relative to the indenter always being the same.