Dear Florian,
As with your present alloy, when we consider metal hardening in the
past we must look at both bulk hardening and surface hardening. In the
former case the hardening would normally be by variation of alloy
content (all systems), work hardening, and heat treatment
This last was primarily via martensitic transformations; cases where
precipitation or order hardening were used are hard to identify
although alloy systems which had the potential were used in the
past.
Surface hardening is another question. Copper alloy artefacts were
often treated in such a way that the final cycles of cold work affected
the surface much more than the core giving a hardened surface over a
softer, toughter core. Copper alloy objects could also get hard
coatings via plating processes. Tin plating copper, bronze or brass can
produce layers of epsilon and/or delta phase and alpha-delta eutectoid
which are hard and corrosion resistant; however, their purpose was
decorative. One way of hardening an iron/steel surface is by
craburisation. I am not an iron specialist and so do not know when
nitriding steel surfaces can first be demonstarted; probably more
recently than popularly believed.
I hope your question stimulates more answeres - it is time for another
look at the topic.
Yours,
Peter Northover
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Peter Northover
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