This week our topic is the first of several on the case hardening of steels. A primer on the basics of selectively heat treating the surface of parts.

First up is the process of nitriding of steels like last week's alloy 135M.  If we add nitrogen to the  surface of an alloy steel part; we can form a thin but very hard and wear resistant layer.

That is a useful thing to have on the contact areas of gears and bearings.

Several methods can be used to create the nitrogen enriched surface

If we heat the part to sufficient temperature in an environment high in nitrogen, it will diffuse into the steel surface. Elevated temperature is required to achieve an acceptable rate of diffusion and amount of nitrogen that can be absorbed.

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