Case Hardening of Steel

Case hardening is defined as a process by which a ferrous material is hardened in such a manner that the surface layer, known as the case, becomes substantially harder than the remaining material, known as the core. This article discusses the equipment required, process variables, carbon and hardness gradients, and process procedures of different types of case hardening methods: carburizing (gas, pack, liquid, vacuum, and plasma), nitriding (gas, liquid, plasma), carbonitriding, cyaniding and ferritic nitrocarburizing. An accurate and repeatable method of measuring case depth is essential for quality control of the case hardening process and for evaluation of workpieces for conformance with specifications. The article also discusses various case depth measurement methods, including chemical, mechanical, visual, and nondestructive methods.