Non-destructive testing of additively manufactured steel components
Kiviluoma, Mika (2019)
2019
Materiaalitekniikan DI-ohjelma - Degree Programme in Materials Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Hyväksymispäivämäärä
2019-09-03
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-201910023658
https://urn.fi/URN:NBN:fi:tuni-201910023658
Tiivistelmä
Additive manufacturing (AM) is a relatively new manufacturing method, which is capable of producing complex geometries and parts on-demand from multiple different materials. Metal AM, with all its advantages, has some challenges as well, many of which are related to residual stresses (RS) generated in the component during manufacturing.
In this work a literature study into the current state of the art of metal AM and especially laser powder bed fusion (L-PBF) is performed. Additionally L-PBF manufactured simple 316L steel components with different post process treatments are characterized both non-destructively and destructively and the results are compared to previous studies. Similarly, more complex 316L rapid mixing nozzles are characterized. The stress corrosion cracking (SCC) properties of AM 316L are also studied.
It is shown that x-ray diffraction (XRD) is a suitable non-destructive testing (NDT) method for characterizing the stress states of AM 316L components. Visual observations and RS depth profiles from the simple AM samples show RS states, which correspond to previous results. Microstructures of AM samples after different post process treatments are also as expected. Martensite transformation due to plastic deformation in AM samples is studied, but cannot be confirmed. No SCC is detected during testing.
An expected compressive RS state is found at the surfaces of the mixing nozzles. Below the surface of one of the nozzles, the stress state changes to anisotropic tension. Possible reasons for this are discussed. The microstructure of the nozzle is as expected. The behavior of the materials of the two sample sets are compared and discussed.
In this work a literature study into the current state of the art of metal AM and especially laser powder bed fusion (L-PBF) is performed. Additionally L-PBF manufactured simple 316L steel components with different post process treatments are characterized both non-destructively and destructively and the results are compared to previous studies. Similarly, more complex 316L rapid mixing nozzles are characterized. The stress corrosion cracking (SCC) properties of AM 316L are also studied.
It is shown that x-ray diffraction (XRD) is a suitable non-destructive testing (NDT) method for characterizing the stress states of AM 316L components. Visual observations and RS depth profiles from the simple AM samples show RS states, which correspond to previous results. Microstructures of AM samples after different post process treatments are also as expected. Martensite transformation due to plastic deformation in AM samples is studied, but cannot be confirmed. No SCC is detected during testing.
An expected compressive RS state is found at the surfaces of the mixing nozzles. Below the surface of one of the nozzles, the stress state changes to anisotropic tension. Possible reasons for this are discussed. The microstructure of the nozzle is as expected. The behavior of the materials of the two sample sets are compared and discussed.