What is the difference between TCD and ECD?
A. These two methods of case depth evaluation are typically used to define case depths of alloy and tool steel grades in which a significant case hardness profile exists and a functional hardness at depth may be required or specified. Total Case Depth (TCD) is defined as the depth at which the case hardness is equivalent to 50 Vickers points (typically) above the core hardness of the material. Effective Case Depth (ECD) is defined as a depth at which a minimum specified hardness value is achieved. The nitrided case (or diffusion zone) may also be optically measured after chemical etching. This method is more suitable for lower alloy materials or hardness gradients not readily discernable by hardness traverse methods such as low carbon, HSLA or stainless steels.
