The Heat Treat Doctor

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Gas carbonitriding is a modified form of the carburizing process and is not a form of nitriding. In this process, both carbon (C) and nitrogen (N) are introduced into the surface of the steel by introducing ammonia (NH3) and a hydrocarbon enriching gas into the furnace atmosphere in order to add nitrogen to the carburized case as it is being produced.

The father of the endothermic gas generator was a gentleman by the name of Norbert K. Koebel, who was fond of saying to young engineers such as The Doctor, “Treat ‘em right and they’ll treat you right.”

Most heat treaters are aware of many failure phenomena, perhaps the most well-known of which is hydrogen embrittlement (aka hydrogen-assisted cracking). But there are several other types, such as liquid-metal embrittlement, that we must understand as well. Let’s learn more.

The nitriding process begins at the surface of the part with the formation of a compound (aka white) layer, which depends to a large extent on the composition of the steel (in particular, the carbon content).

Retrogression heat treatment and re-aging (RRA) is used for retaining optimal strength in aluminum alloys while avoiding stress corrosion cracking (SCC). Last time, we learned about the SCC phenomenon and its effects on aluminum alloys.

We live in the real world, and things break down or otherwise drift from factory settings. Patchwork repairs (that all too often become permanent) and temporary fixes are poor substitutes for properly planned and well-executed maintenance activities.

Extractive metallurgy is an area of our science that deals with the process and methods of gathering and isolating metals from their ores (i.e., natural mineral deposits) and in some instances refining them.

Sometimes learning more about a common heat-treat phenomenon can yield a deeper understanding of the underlying principles involved.