PSI - Issue 51

Milan Uhríčik et al. / Procedia Structural Integrity 51 (2023) 166 – 172 M. Uhrí č ik et al. / Structural Integrity Procedia 00 (2022) 000–000

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a

Fig. 7. Fractures of austenitic steel AISI 304 after plasma nitriding after the fatigue test; (a) striations; (b) secondary cracks and dimples.

b

Authors Ç etinarslan et al. (2012) write in their articles that samples after nitriding endured a smaller number of cycles than samples without nitriding. In our case it was the opposite, the plasma nitriding process caused a longer fatigue life under the same load conditions. However, fatigue tests performed by Ç etinarslan et al. (2012) were tensile fatigue tests. 4. Conclusion For fatigue tests, by three-point cyclic bending, samples were used in the initial state and after plasma nitriding. These fatigue tests showed that nitride samples had a higher number of cycles to fracture. Observed fracture areas of samples by SEM were not that different. Crack initiations started at the corners of samples, the fatigue area and the static failure area had approximately the same areas in both samples. This fractographic analysis did not show a significant influence of the nitriding layer on the start of crack initiation and overall fracture, during fatigue tests. More fatigue test will be needed to determine the effect of plasma nitriding on fracture mechanisms in austenitic steels.