in contrapposizione a "deep case", come contenitore interno, il quale a sua volta racchiude il "core".

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Ho consultato Internet e le due pagine in riferimento recitano così:

A.
Nitriding
(Shallow and Deep Case)

The process of adding nitrogen to the surface of steel parts, using dissociated ammonia as the source. Gas Nitriding develops a very hard case after long time at comparatively low temperature, without quenching.

The process is carried out below the transformation temperature of alloy steels, so that there is no distortion caused by the transformation of the metal. Parts to be nitrided are pre-hardened to the proper strength level, then nitrided at a temperature where the base metal properties are not affected. As a result, a very high strength product with extremely good wear resistance can be produced, with little to no dimensional change.

B.
Carburizing
(Shallow and Deep Case)

A heat treatment that increases strength and wear resistance at moderate cost.

Carburizing increases strength and wear resistance by diffusing carbon into the surface of the steel creating a “case” while retaining a substantially lesser hardness in the “core”. This treatment is applied to low carbon steels after machining.

Strong and very hard-surface parts of intricate and complex shapes can be made of relatively lower cost materials that are readily machined or formed prior to heat treatment.



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Poi ho consultato il McGrawHill, che riporta:

nitriding
[METALL] cementazione nitrica; nitrurazione
Surface hardening of steel by formation of nitrides; nitrogen is introduced into the steel usually by heating in gaseous ammonia.

case
[METALL] strato cementato
Outer layer of a ferrous alloy which has been made harder than the core by case hardening.


Certo, non ho la traduzione da darti, ma spero che queste indicazioni possano aiutarti a comprendere.