Influence of Surface Finish on High Cycle Fatigue Behaviour of a 304l Austenitic Stainless Steel

The aim of the study is to determine the influence of surface parameters on the high cycle fatigue behaviour of a 304L austenitic stainless steel. These parameters are of two types: mechanical (roughness, residual stresses) and microstructural (strain-hardening and phase transformation). For the need of the study, different surfaces have been prepared, using turning, grinding or polishing. These preparations, depending on the machining severity, have led to rugosities or hardening more or less important, and to the introduction of tensile residual stresses more or less severe. One turning condition have led to a partial transformation of the initial austenite into martensite.

In order to determine the importance of these parameters, fatigue tests have been performed at room temperature for a positive stress ratio (R = 0.05) on samples presenting the above-mentioned surface preparations. The comparison of the responses of the different samples shows that the polished ones have a greater fatigue performance than the others: the fatigue limit is lowered of nearly 15% when specimens are turned or ground.

The influence some parameters may have on the fatigue resistance is discussed here. Some observations are also made in order to explain the differences observed between the samples.