Ferritic stainless steels are prone to grain coarsening and precipitation of chromium-rich grain boundary phases during fusion welding, which increase intergranular corrosion susceptibility. State-of-the-art techniques to overcome these challenges mainly feature heterogeneous nucleating agents with regard to grain coarsening or alternating alloy concepts as well as post-weld heat treatments as for restoration of intergranular corrosion resistance. The present investigation seeks to depart from these traditional approaches through the use of a tailored heat input during pulsed laser beam welding by means of free-form pulse shaping. Grain size analysis using electron backscatter diffraction shows a substantial reduction of grain size as compared to continuous-wave lasers due to a distinctive columnar to equiaxed transition. Moreover, phase analyses reveal the overcoming of chromium carbide precipitation within the heat-affected zone. As corrosion tests demonstrate, intergranular attack is therefore concentrated on the weld metal. In comparison to continuous-wave laser beam welding, intergranular corrosion susceptibility is substantially reduced for very short pulse durations. From these results, it can be derived that pulsed laser beam welding using free-form pulse shaping enables direct control of heat input and, thus, tailored grain growth and precipitation formation properties.
@article{doi:10.17170/kobra-202301267424,
author ={Sommer, Niklas and Stredak, Florian and Wiegand, Michael and Böhm, Stefan},
title ={Grain growth and precipitation behaviour of AISI 430 ferritic stainless steel subjected to pulsed laser beam welding using free-form pulse shaping},
keywords ={600 and Ferritischer Stahl and Edelstahl and Laserschweißen and Impulslaser and Interkristalline Korrosion and Kornwachstum and Kornfeinung and Ausscheidung},
copyright ={http://creativecommons.org/licenses/by/4.0/},
language ={en},
journal ={Welding in the World},
year ={2022-10-26}
}