Comparison of Various Methods for Specifying and Determining the Case Depth of Nitrided Components

The use of nitriding to improve the surface hardness of various components continues to increase across the industry. However, no universally accepted definition of “case depth” is available to allow the comparison of different nitriding processes and cycles. This study documents the current published methods of specifying and determining case depth for nitrided components, and discusses the impact of these different methods with respect to wear, case crushing, and bending fatigue performance. Various hardness profiles for common nitriding alloys will be evaluated against potential subsurface shear stresses, in an effort to determine an optimal and robust method of specifying case depth.