Why Heat Treat Only the Surface of Metals?

[influx]

Why is it sometimes necessary to heat treat the surface and not the core? I.E. Why are surface hardening processes used? I tried to Google but to no avail. Thanks.

 

[SteamKing]

Why is it sometimes necessary to heat treat the surface and not the core? I.E. Why are surface hardening processes used? I tried to Google but to no avail. Thanks.

You need to improve your googling skills. This will help you tremendously in the future.

Surface hardening can be performed for a variety of reasons. It may be related to the appearance of the finished product, to prevent the formation of tiny cracks in the surface which could grow and eventually cause failure, etc.

Here is an article which your search should have turned up:

http://en.wikipedia.org/wiki/Case_hardening