Microstructural pecularities in the surface of case-hardened components

The negative influence of the surface-near structure of case-hardened compo nents as caused by the pick-up of non-metallic elements from the carburisin g atmosphere is a well-known fact. The most prominent effect produced by ox ygen is the so-called internal oxidation, which reduces by oxide formation the amount of dissolved alloying elements manganese, chromium and silicone, resulting in a respective hardenability loss. The present work presents mi croscopical and spectroscopical possibilities for specifying the different forms of appearance of the internal oxidation, as well as critical reflecti ons on their evaluation. In addition, a somewhat less known, negative influ ence of the loss of hardenability inflicting alloying elements on the outer part of the case structure is mentioned, which is found in low-pressure ca rburising with or without plasma support.