HIGH-INTENSITY PULSED LASER EFFECTS ON THE SLM 316L ALLOY

Abstract

Austenitic stainless steel 316L is widely used because of its favorable mechanical properties up to 600°C, good ductility, corrosion and oxidation resistance, lower cost. Some of its applications include construction, automobile industry, implants, parts for nuclear fission reactor (for example cooling channels). 316L and 316L-based ODS (oxide dispersion strengthened) steel also have a potential for application in future fusion reactors as construction materials. From this aspect, investigation was conducted on the behavior of 316L parts obtained by contemporary technique of selective laser melting (SLM) under the effect of high heat fluxes (HHF) obtained by high-intensity laser pulses. Namely, fusion reactor materials are, among other, exposed to high thermal loads which can be, in one approximation, simulated by lasers. This is a relatively novel approach in fusion material studies, scarcely reported in literature. Pulses in picosecond (ps) time domain were employed and radiation intensities were of the order of 10¹⁰-10¹¹ W/cm², while irradiation was conducted in the ambience of vacuum. 316L austenitic stainless steel parts in our work were fabricated by SLM technique using fixed laser scanning parameters. Mechanical properties of the obtained samples were determined by indentation hardness tester and tensile tests. Measured microhardness was HV_0.3=220, UTS=686 MPa, σ_0.2=536 MPa, and elastic modulus E=39.9 GPa. Obtained morphological, structural, mechanical and chemical changes were analyzed depending on the irradiation conditions. Damages due to ps laser pulses were deep, with small diameter and well defined edges due to low heat effect. Damage threshold was estimated depending on the number of pulses applied and for 500 pulses in ps domain it was approximately estimated to be ~1.8 J/cm². Surface of the samples after laser irradiation was characterized by indentation hardness tester, optical microscope and scanning electron microscope. The obtained results are expected to provide better understanding of HHF-induced surface features on the materials, which will lead to their further improvement and potential functionality for fusion applications.

Acknowledgement. This research was supported by the Science Fund of the Republic of Serbia, Grant No. 7365, Development of dispersion-strengthened metal-based materials for applications in fusion reactor - DisSFusionMat; and by the Ministry of Education, Science and Technological Development of the Republic of Serbia, Contract No. 451-03-136/2025-03/200017.