Internal Oxidation Process

ASM Heat Treating Society                

Internal Oxidation Process At a given temperature during gas carburizing, the oxygen content and the depth of oxygen penetration are strongly influenced by the oxygen potential of the atmosphere (the limiting oxygen potential being that at which iron begins to oxidize). However, as the carbon potential rises, the oxygen potential falls. Consequently, with high carbon-potential carburizing, the oxidizing effect is reduced depending on the duration of carburizing. In commercial case-hardening steels, the depths at which oxides are detected using conventional optical microscopy typically are less than 25 µm (I.e., for carburized total case depths of 1 to 2 mm). Deeper cases will produce deeper penetrating oxides; for example, an 8 mm total case depth in a Cr-Ni-Mo steel would likely have an oxide penetration depth of 75 to 100 µm.