Page 211 - Materials Chemistry, Second Edition

198 3 Metals

Figure 3.26. Schematic of (a) martempering and (b) austempering processes for steel. Courtesy of the
International Steel Group and Mittal Steel Company (http://www.mittalsteel.com).

of the surface using flame, induction, laser, electron beam, or ion bombardment.
Strengthening occurs through either grain size reduction or solute hardening, but
occurs only on the periphery of the material due to the controlled, limited exposure.