High-Speed Laser Cladding on Thin-Sheet-Substrates—Influence of Process Parameters on Clad Geometry and Dilution

Abstract

Laser-based Directed Energy Deposition (DED-LB) represents a production method of growing importance for cladding and additive manufacturing through the use of metal powders. Yet, most studies utilize substrate materials with thicknesses of multiple millimeters, for which laser cladding of thin-sheet substrates with thicknesses less than 1 mm have only been scarcely studied in the literature. Most studies cover the use of pulsed laser sources, since sheet distortion due to excess energy input is a key problem in laser cladding of thin-sheet substrates. Hence, the authors of the present investigation seek to expand the boundaries of cladding thin-sheet substrates through the use of a high-speed laser cladding approach which utilizes a continuous-wave, ytterbium fiber laser and traverse speeds of 90 mms−1 to clad stainless steel sheets with a thickness of 0.8mm. Furthermore, fundamental process–property relationships for the target values of clad width, clad height, and dilution depth are studied and thoroughly discussed. Additionally, process maps for the target values are established based on manifold experiments, and the significance of process parameters on target values is studied using analysis of variance. The results demonstrate that clad widths as high as 1413 μm and dilution depths as low as 144 μm can be obtained by high-speed laser cladding of thin-sheet substrates. Thus, pathways toward thin-sheet substrates with enhanced performance are opened.

A Novel Approach to Inhibit Intergranular Corrosion in Ferritic Stainless Steel Welds Using High-Speed Laser Cladding

“…(a) Chemical composition of AISI 430 and AISI 430Ti sheet material used in the investigation, adopted from [31]. Copyright 2020 Niklas Sommer; (b) Chemical composition of AISI 316L austenitic stainless steel powder, partially adopted from [37] Nominal distribution 20-53 µm, partially adopted with permission from ref. [37].…”

“…Copyright 2020 Niklas Sommer; (b) Chemical composition of AISI 316L austenitic stainless steel powder, partially adopted from [37] Nominal distribution 20-53 µm, partially adopted with permission from ref. [37]. Copyright 2021 Niklas Sommer.…”

“…The usage of focusing lenses with focal lengths of 200 mm and 300 mm yielded approximate beam diameters of 0.8 mm and 1.2 mm on the workpiece, respectively. Based on prior investigations on high-speed laser cladding of thin-sheet substrates [37], the nozzle standoff distance was kept at 12 mm throughout the experiments, while the laser focus was set to the substrate surface. For a continuous powder feed to the cladding optics, a two-disc powder feeder (GTV PF2/2, GTV Verschleißschutz GmbH, Luckenbach, Germany) using argon carrier gas (grade 4.6, purity ≥ 99.996 %) at a flow rate of 5 L • min −1 was employed.…”

“…For a continuous powder feed to the cladding optics, a two-disc powder feeder (GTV PF2/2, GTV Verschleißschutz GmbH, Luckenbach, Germany) using argon carrier gas (grade 4.6, purity ≥ 99.996 %) at a flow rate of 5 L • min −1 was employed. The powder mass flow was set to 24 g • min −1 for the cladding experiments based on prior investigations [37]. Moreover, argon shielding gas (grade 4.6, purity ≥ 99.996 %) with a flow rate of 10 L • min −1 was fed through the coaxial outlet of the powder-nozzle to prevent oxidation of the clad.…”

“…Figure 5 depicts the etched micrographs of the laser-cladded AISI 430 and AISI 430Ti welds. As can be derived from the microscopy images, previously developed process windows for the high-speed laser cladding of thin-sheet substrates [37] could successfully be transferred to the welded substrates and allowed for a reproducible and centrically aligned coating of the weld seam. In addition to the varying clad width, which could be anticipated based on the altering laser beam diameter, a variation in dilution with the substrate material can be detected.…”