Influence of Printing Strategy on Fatigue and Microstructural Properties of LPBF-Manufactured 16MnCr5

Sammanfattning

This master thesis evaluates the very high cycle fatigue performance of two printing strategies using laser powder bed fusion with 16MnCr5 powder. The first method, “bulk-printed”, had specimens cut from a printed block, while the second, “free-printed”, were produced in the final specimen geometry. Two series were produced from each printing method, hardened and as-built. The as-built samples were of academic interest and documented for hardness and microstructure. The hardened series were evaluated for hardness, microstructure, fatigue performance, and fractography. Fatigue testing showed that the free-printed series exhibited approximately 30% higher fatigue strength compared to the bulk-printed series. The effect of near-surface properties was discussed as being a cause of the difference, the most probable being laser contouring. A SEM fractography review concluded that all fractures initiated at subsurface pores and unmelted regions. LOM results showed no differences in microstructure within or between the samples that shared the same thermal history.