Influence of oxynitride layer on the deep-drawing sheets fatigue properties

The paper deals with the influence of nitrooxidation on fatigue lifetime of low carbon deep drawing steel DC 01 EN 10130 - 91 delivered in the form of sheets. Fatigue results were determined at high - frequency fatigue machine (f ≈ 20 kHz), at T = 20 š3°C using bending loading with stress ratio R = -1. It was found that the nitrooxidation process has positive effect on the fatigue lifetime compared with base material. The structure analyze and measurement of microhardness of steel sheets after nitrooxidation process was also performed. The Fe2O3 and Fe3O4 as well as the layer of ε - phase (Fe3N) were identified in surface and subsurface layers and nitrides Fe4N and Fe16N2 were segregated in ferritic matrix. The maximum microhardness was determined in diffusion area containing the slight nitrides of Fe16N2 uniformly distributed in ferritic matrix.