In-Line Observation of Laser Cladding Processes via Atomic Emission Spectroscopy

Schmidt, Martín; Huke, P.; Gerhard, Christoph; Partes, Knut

doi:10.3390/ma14164401

Cited by 8 publications

(4 citation statements)

References 37 publications

(33 reference statements)

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“…Higher energy input led to increasing vaporisation and the depletion of Cr atoms from the melt pool [29]. Similar effects could be observed during a recently published study [30]. Co-Cr-powder was cladded on mild steel substrate with a coaxial powder nozzle and a 4 kW diode laser.…”

Section: Optical Emission Spectroscopy (Oes) In Laser Welding Processessupporting

confidence: 79%

See 1 more Smart Citation

Laser Cladding With Combined NIR and Blue Diode Laser Including In-Line Atomic Emission Spectroscopy

Schmidt

Kohler²,

Gerhard

et al. 2023

Lasers Manuf. Mater. Process.

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For Directed Energy Deposition processes (DED) lasers in the near infrared (NIR) as well as in the infrared (IR) range are predominantly used. Recent developments have also made high-power lasers in the visible spectrum available. As the DED process is used for cladding of surfaces, repairing and additive manufacturing of components, process monitoring and control methods are necessary to ensure a consistent manufacturing quality. Optical emission spectroscopy (OES) of the process radiation can provide information on process conditions and the deposition layer during DED processes. However, DED processes are in the heat conduction regime and superimposed broad spectral emissions dominate the wavelength specific signals. The object of this work is to compare the process behavior using a NIR and blue diode laser separately as well as in combination. The influence of the laser wavelength on the cladding result as well as on the emitted process radiation is to be determined. Therefore, single tracks of Co-based powder (MetcoClad21) were clad on an S235 base material by using each laser source separately as well as in combination. Both laser beams were combined within a single hybrid optic. While the scan speed and powder feed rate remained constant, the laser power was varied. Single spectra have been recorded from the process using a spectrometer. Single spectra are sorted and element lines were identified. Only non-ionised elements could be detected, with chromium appearing frequently. It was shown that comparable results in terms of cladding quality can be produced independently from the laser wavelength. In fact, less laser power (app. 30% less, 1 kW at 980 nm (NIR) compared to 0.7 kW at 450 nm (blue)) was needed aiming for comparable results in geometrical factors (as dilution, height, depth, width) and homogeneity (chemical composition distribution) by using blue laser irradiation. Furthermore, more spectrometric signals (approx. 2–28 times more) were detected compared to experiments using only NIR irradiation with the same laser power. This effect is particularly high at low laser powers and decreases with increasing power. Hence, it is possible to enable in-line process analysis by adding blue laser irradiation to the mix of the beam.

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Section: Optical Emission Spectroscopy (Oes) In Laser Welding Processessupporting

confidence: 79%

“…Single spectra are sorted into two categories -Type-A and Type-B. This has been published in previous work [30]. Type-A spectra show at least one detectable peak whereas Type-B spectra merely feature thermal background radiation without any detectable peaks.…”

Section: Spectroscopic Measurementsmentioning

confidence: 99%

Laser Cladding With Combined NIR and Blue Diode Laser Including In-Line Atomic Emission Spectroscopy

Schmidt

Kohler²,

Gerhard

et al. 2023

Lasers Manuf. Mater. Process.

Self Cite

View full text Add to dashboard Cite

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“…In contrast, chromium is predominantly contained in the powder material (26.7 wt.%) and only to a negligible extent in the substrate material (0.03 wt.%). In a previous study (Ref 20), it was already found that emission lines occur mainly in the presence of a melt pool. Experiments with an isolated laser-powder interaction showed no significant emissions.…”

Section: Cross-sectional Dimensions and Spectroscopic Analysismentioning

confidence: 91%

Investigation of Direct Metal Deposition Processes Using High-Resolution In-line Atomic Emission Spectroscopy

et al. 2022

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Process monitoring and control methods during direct metal deposition (DMD) ensure consistent manufacturing quality of the product. Naturally occurring optical process emissions provide selective and specific element lines, which can be investigated by optical spectrometers. However, DMD processes are mainly characterized by thermal conduction. Hence, the resulting optical emission lines have low intensities. The aim of this work is to investigate the spectral lines and determine the required resolution of the spectrometer. Two spectrometers coupled by a bifurcated optical fiber were used simultaneously (resolution = approx. 47 pm FWHM at 522 nm and 55 pm FWHM at 407.5 nm and resolution = 0.73 nm FWHM). A parameter study with varying process parameters using Co-Cr-based (MetcoClad21) powder on low-alloyed tool steel C45W (1.1730) substrate material was conducted. Peaks occurring in spectral data were assigned to specific element emission lines by using data from the NIST atomic spectra database. All identified element lines were non-ionized elements. Cr I, Fe I and Mn I lines in particular were frequently observed. The occurrence of element emission lines as well as the peak intensity ratios for specific elements was compared with the cross-sectional dimensions including height, weld depth and dilution. It has been shown that the occurrence and intensity of emission lines correlate with the process parameters, especially the laser power. Furthermore, the dilution of a deposition track correlates with the occurrence and intensity of an identified Fe I emission line, represented by a Fe-Cr peak intensity ratio.

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“…The relationship model between the elements' weight ratio and the intensity ratio of spectral lines was built, which indicated that the elements' weight ratio in the coating was directly affected by the variation of input energy density during processing. Schmidt et al [11] used a spectrometer to measure the light emission during laser cladding and identify the element lines in the spectrum. The results revealed that the measurement of line or spectral intensity can be used for on-line monitoring of the laser cladding dynamic process.…”

Section: Introductionmentioning

confidence: 99%

Research of On-Line Monitoring Technology Based on Laser Triangulation for Surface Morphology of Extreme High-Speed Laser Cladding Coating

Wang

Guo

et al. 2023

Coatings

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This work aims to develop a novel method for on-line monitoring of coating quality during the Extreme High-speed Laser Cladding (EHLA) process. JG-11 coating was prepared by EHLA, and microstructure, microhardness, corrosion performance, and scratch resistance were investigated. To analyze the influences of fluctuations in processing parameters on coating quality, a single-factor experiment scheme was designed and an on-line monitoring system based on laser triangulation was built. Furthermore, a new forming method for the surface profile of EHLA coating was proposed, and a new comprehensive evaluation index of surface morphology was accordingly designed. Benefitting from the extremely high cooling rate, EHLA JG-11 coating had fine grains, high hardness, and better corrosion resistance and scratch resistance than those of Electroplating Hard Chromium (EHC). The results revealed that the surface morphologies presented different characteristics due to the fluctuations of process parameters, such as high surface flatness, deep pits, small peaks, poor directionality, etc. The comprehensive evaluation index composed of Sa, Ssk, and Str could effectively characterize the surface morphology of EHLA coating, which proved that the monitoring system and evaluation method could realize on-line monitoring of the process parameters during the EHLA process.

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In-Line Observation of Laser Cladding Processes via Atomic Emission Spectroscopy

Cited by 8 publications

References 37 publications

Laser Cladding With Combined NIR and Blue Diode Laser Including In-Line Atomic Emission Spectroscopy

Laser Cladding With Combined NIR and Blue Diode Laser Including In-Line Atomic Emission Spectroscopy

Investigation of Direct Metal Deposition Processes Using High-Resolution In-line Atomic Emission Spectroscopy

Research of On-Line Monitoring Technology Based on Laser Triangulation for Surface Morphology of Extreme High-Speed Laser Cladding Coating

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