Classification of Case Hardening

Classification of Case Hardening Case hardening-the production of parts that have hard, wear-resistant surfaces, but with softer and/or tougher cores-can be accomplished using two distinct methods.

One approach is to use a grade of steel that already contains sufficient carbon to provide the required surface after heat treatment. The surface areas requiring the higher hardness are then selectively heated and quenched. The second method is to use a steel that normally is not capable of being hardened to the desired degree, then alter the composition of the surface layers by diffusion so it either can be hardened or, in some instances, becomes hard during processing. Precise classification of case hardening is difficult, but for most practical purposes, case hardening treatments can be broadly classified into four groups including carburizing, carbonitriding, nitriding, and nitrocarburizing.